Fixed MR widget content wrapping for XS viewports

Update merge_requests.scss

Update merge_requests.scss to use padding shorthand

Removed padding from Accept Merge Request button

app/assets/stylesheets/pages/merge_requests.scss

@@ -129,6 +129,11 @@
         margin-bottom: 4px;
       }
+      .btn-grouped {
+        float: none;
+        margin-right: 0;
+      }
+
       .accept-action {
         width: 100%;
         text-align: center;

changelogs/unreleased/25202-fix-mr-widget-content-wrapping.yml

+---
+title: Centered Accept Merge Request button within MR widget and added padding for
+  viewports smaller than 768px
+merge_request: 
+author: Ryan Harris