Fixes #14443: Only transition what needs transitioning for thumbnails to avoid...

Fixes #14443: Only transition what needs transitioning for thumbnails to avoid Safari/Chrome render bug

dist/css/bootstrap.css

@@ -4680,9 +4680,9 @@ a.list-group-item.active > .badge,
   background-color: #fff;
   border: 1px solid #ddd;
   border-radius: 4px;
-  -webkit-transition: all .2s ease-in-out;
-       -o-transition: all .2s ease-in-out;
-          transition: all .2s ease-in-out;
+  -webkit-transition: border .2s ease-in-out;
+       -o-transition: border .2s ease-in-out;
+          transition: border .2s ease-in-out;
 }
 .thumbnail > img,
 .thumbnail a > img {

less/thumbnails.less

@@ -12,7 +12,7 @@
   background-color: @thumbnail-bg;
   border: 1px solid @thumbnail-border;
   border-radius: @thumbnail-border-radius;
-  .transition(all .2s ease-in-out);
+  .transition(border .2s ease-in-out);
 
   > img,
   a > img {