Move swipe diff border to the right

In the Vue image diff app, the border needs to be on the right because
the new image comes in from the left. The old image diff app which is
used in commits and compare views had the new image visible by default
and hiding away from the left.

app/assets/stylesheets/pages/diff.scss

@@ -154,11 +154,17 @@
 
       .swipe-wrap {
         overflow: hidden;
-        border-left: 1px solid $gl-gray-400;
+        border-right: 1px solid $gl-gray-400;
         position: absolute;
         display: block;
         top: 13px;
         right: 7px;
+
+        &.left-oriented {
+          /* only for commit view (different swipe viewer) */
+          border-right: 0;
+          border-left: 1px solid $gl-gray-400;
+        }
       }
 
       .swipe-bar {

app/views/projects/diffs/_replaced_image_diff.html.haml

@@ -37,7 +37,7 @@
     .swipe-frame
       .frame.deleted
         = image_tag(old_blob_raw_url, alt: diff_file.old_path, lazy: false)
-      .swipe-wrap
+      .swipe-wrap.left-oriented
         = render partial: "projects/diffs/image_diff_frame", locals: { class_name: "added js-image-frame #{class_name}", position: position, note_type: DiffNote.name, image_path: blob_raw_url, alt: diff_file.new_path }
       %span.swipe-bar
         %span.top-handle