Remove fomantic image module (#21145)

Remove this small, but unnecessary
[module](https://fomantic-ui.com/elements/image.html) and use `img`
selector over previous `.image`. Did a few tests, could not notice any
visual regression.

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lauris BH <lauris@nix.lv>

web_src/less/features/gitgraph.less

@@ -134,7 +134,7 @@
       padding-bottom: 1px;
     }
 
-    .author .ui.avatar.image {
+    .author img.ui.avatar {
       width: auto;
       height: 18px;
       max-width: none;