Always use HTML attributes for avatar size (#31509)

Many avatars were rendered in HTML with certain width/height but then
resized again in CSS. This was pointless so I removed all these cases
and made the HTML size match the previous render size.

Also did a few CSS cleanups in the tribute rendering:

<img width="648" alt="image"
src="cb2fafb3-5e20-46e9-814f-07df20038beb">

web_src/css/modules/comment.css

@@ -50,10 +50,6 @@
   background: none;
 }
 
-.ui.comments .comment .avatar {
-  width: 30px;
-}
-
 .ui.comments .comment > .content {
   display: flex;
   flex-direction: column;