Merge branch 'css-zero-unit-again' into 'master'

Fix a few remaining uses of `0px`.

See #14299 for more information.

cc: @jschatz1 

See merge request !3310

app/assets/stylesheets/framework/avatar.scss

@@ -16,7 +16,7 @@
   }
 
   &.group-avatar, &.project-avatar, &.avatar-tile {
-    @include border-radius(0px);
+    @include border-radius(0);
   }
 
   &.s16 { width: 16px; height: 16px; margin-right: 6px; }

app/assets/stylesheets/framework/selects.scss

@@ -41,7 +41,7 @@
 }
 
 .select2-drop {
-  @include box-shadow(rgba(76, 86, 103, 0.247059) 0px 0px 1px 0px, rgba(31, 37, 50, 0.317647) 0px 2px 18px 0px);
+  @include box-shadow(rgba(76, 86, 103, 0.247059) 0 0 1px 0, rgba(31, 37, 50, 0.317647) 0 2px 18px 0);
   @include border-radius ($border-radius-default);
   border: none;
 }

app/assets/stylesheets/pages/projects.scss

@@ -37,7 +37,7 @@
       .dropdown-menu {
         left: auto;
         width: auto;
-        right: 0px;
+        right: 0;
         max-width: 240px;
       }
     }