Merge branch 'new-merge-request-commit-box-fix' into 'master'

Fixed styling of commit box in new MR

## What does this MR do?

Fixes an issue that caused the new merge request commit box to go all funny styled.

## What are the relevant issue numbers?

#18781 

## Screenshots (if relevant)

![Screen_Shot_2016-06-17_at_14.08.44](/uploads/b1e34b0c6bf67adc1be8748306e20b06/Screen_Shot_2016-06-17_at_14.08.44.png)

See merge request !4747

app/assets/stylesheets/pages/merge_requests.scss

@@ -244,6 +244,10 @@
   .panel-footer {
     padding: 5px 10px;
+
+    .btn {
+      min-width: auto;
+    }
   }
   .commit {
@@ -252,9 +256,7 @@
     }
     .avatar {
-      width: 20px;
-      height: 20px;
-      margin-right: 5px;
+      margin-left: 0;
     }
     .commit-row-info {