Merge branch 'enable-scss-lint-trailing-whitespace' into 'master'

Enable trailingWhitespace in scss-lint

## What does this MR do?
Enables `trailingWhitespace` in `.scss-lint.yml`

## Are there points in the code the reviewer needs to double check?
None

## Why was this MR needed?
Improve SCSS maintainability and consistency

## Screenshots (if relevant)
None

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
#23485 

See merge request !7077

.scss-lint.yml

@@ -223,7 +223,7 @@ linters:
   # Reports lines containing trailing whitespace.
   TrailingWhitespace:
-    enabled: false
+    enabled: true
   # Don't write trailing zeros for numeric values with a decimal point.
   TrailingZero:

app/assets/stylesheets/framework/animations.scss

 // This file is based off animate.css 3.5.1, available here:
 // https://github.com/daneden/animate.css/blob/3.5.1/animate.css
-// 
+//
 // animate.css - http://daneden.me/animate
 // Version - 3.5.1
 // Licensed under the MIT license - http://opensource.org/licenses/MIT
-// 
+//
 // Copyright (c) 2016 Daniel Eden
 .animated {

app/assets/stylesheets/framework/logo.scss

@@ -61,7 +61,7 @@
         10%, 80% {
           fill: $tanuki-red;
         }
- 
+
         20%, 90% {
           fill: lighten($tanuki-red, 25%);
         }

app/assets/stylesheets/pages/cycle_analytics.scss

@@ -9,15 +9,15 @@
       padding: 24px 0;
       border-bottom: none;
       position: relative;
-      
+
       @media (max-width: $screen-sm-min) {
         padding: 6px 0 24px;
-      } 
+      }
     }
     .column {
       text-align: center;
-      
+
       @media (max-width: $screen-sm-min) {
         padding: 15px 0;
       }
@@ -36,7 +36,7 @@
       &:last-child {
         text-align: right;
-        
+
         @media (max-width: $screen-sm-min) {
           text-align: center;
         }
@@ -51,7 +51,7 @@
   .bordered-box {
     border: 1px solid $border-color;
     border-radius: $border-radius-default;
-  
+
   }
   .content-list {
@@ -73,10 +73,10 @@
           font-weight: 600;
           color: $gl-title-color;
         }
-        
+
         &.text {
           color: $layout-link-gray;
-          
+
           &.value-col {
             color: $gl-title-color;
           }
@@ -108,13 +108,13 @@
     .svg-container {
       text-align: center;
-      
+
       svg {
         width: 136px;
         height: 136px;
       }
     }
-    
+
     .inner-content {
       @media (max-width: $screen-sm-min) {
         padding: 0 28px;

app/assets/stylesheets/pages/diff.scss

@@ -222,12 +222,12 @@
         top: 13px;
         right: 7px;
       }
- 
+
       .frame {
         top: 0;
         right: 0;
         position: absolute;
- 
+
         &.deleted {
           margin: 0;
           display: block;

app/assets/stylesheets/pages/environments.scss

@@ -37,10 +37,10 @@
   .branch-name {
     color: $gl-dark-link-color;
   }
-  
+
   .stop-env-link {
     color: $table-text-gray;
-    
+
     .stop-env-icon {
       font-size: 14px;
     }
@@ -48,11 +48,11 @@
   .deployment {
     .build-column {
-    
+
       .build-link {
         color: $gl-dark-link-color;
       }
-      
+
       .avatar {
         float: none;
       }

app/assets/stylesheets/pages/events.scss

@@ -142,7 +142,7 @@
 .event-last-push {
   overflow: auto;
   width: 100%;
-  
+
   .event-last-push-text {
     @include str-truncated(100%);
     padding: 4px 0;

app/assets/stylesheets/pages/login.scss

@@ -286,7 +286,7 @@
   .new_user {
     position: relative;
     padding-bottom: 35px;
-    
+
     @media (min-width: $screen-sm-min) and (max-width: $screen-sm-max) {
       .forgot-password {
         float: none !important;

app/assets/stylesheets/pages/merge_conflicts.scss

@@ -254,7 +254,7 @@ $colors: (
         border-top: solid 2px $border-green-extra-light;
       }
     }
-    
+
     .editor {
       pre {
         height: 350px;

app/assets/stylesheets/pages/notes.scss

@@ -458,7 +458,7 @@ ul.notes {
 .discussion-next-btn {
   svg {
     margin: 0;
-    
+
     path {
       fill: $gray-darkest;
     }

app/assets/stylesheets/pages/status.scss

@@ -74,7 +74,7 @@
   .ci-status-icon-success_with_warning {
     color: $gl-warning;
   }
-  
+
   .ci-status-icon-running {
     color: $blue-normal;
   }

app/assets/stylesheets/pages/tree.scss

@@ -29,11 +29,11 @@
       .last-commit {
         @include str-truncated(506px);
-        
+
         @media (min-width: $screen-sm-max) and (max-width: $screen-md-max) {
           @include str-truncated(450px);
         }
-        
+
       }
       .commit-history-link-spacer {