Clean up various avatar dimensions (#24701)

Clean up a few cases where avatar dimensions were overwritten via CSS,
which were no longer needed or were possible to set via HTML width.

Also included are two small fixes:

- Fix one more case of incorrect avatar offset on review timeline
- Vertically center avatars in review sidebar

There is more to be done here, but some of the work depends on Fomantic
`comment` module removal, or in the case of org member lists, a refactor
of the `avatarlink` template to accept a size.

<img width="371" alt="image"
src="9c5902fb-2b89-4a7d-a152-60e74c3b2c56">
<img width="306" alt="image"
src="c8d92e2a-91c9-4f4a-a7de-6ae1a6bc0479">

---------

Co-authored-by: Giteabot <teabot@gitea.io>

web_src/css/modules/comment.css

@@ -47,20 +47,8 @@
 }
 
 .ui.comments .comment .avatar {
-  display: block;
-  width: 2.5em;
-  height: auto;
   float: left;
-  margin: 0.2em 0 0;
-}
-
-.ui.comments .comment img.avatar,
-.ui.comments .comment .avatar img {
-  display: block;
-  margin: 0 auto;
-  width: 100%;
-  height: 100%;
-  border-radius: 0.25rem;
+  width: 2.5em;
 }
 
 .ui.comments .comment > .content {