Reduce emoji size (#12317)

* Reduce emoji size

Rendering should now pretty much match GitHub with 1.25em. I verified
that emojis don't increase the line height and removed unecessary size
overrides because now all emojis should appear similar in relation to
the font size.

* fix reaction hover

web_src/less/_repository.less

@@ -2387,7 +2387,7 @@
         .select-reaction {
             display: flex;
             align-items: center;
-            padding: .5rem;
+            padding: 0 .5rem;
 
             &:not(.active) a {
                 display: none;