Remove polluted .ui.right (#26825)

Each change is tested manually line by line. There are too many changes
so I can't share dozens of screenshots.

In short:

1. `ui right` could be still used in `ui top attached header`, because
there is a special case.
2. A lot of `ui right` are just no-op, so they can be removed safely.
3. Some of the `ui right` should be replaced by `gt-float-right` (to
avoid breaking, leave them to the future).
4. A few of the `ui right` could be rewritten by flex.

web_src/js/components/RepoBranchTagSelector.vue

@@ -33,7 +33,7 @@
           <div class="ui label" v-if="item.name===defaultBranch && mode === 'branches'">
             {{ textDefaultBranchLabel }}
           </div>
-          <a v-show="enableFeed && mode === 'branches'" role="button" class="rss-icon ui compact right" :href="rssURLPrefix + item.url" target="_blank" @click.stop>
+          <a v-show="enableFeed && mode === 'branches'" role="button" class="rss-icon gt-float-right" :href="rssURLPrefix + item.url" target="_blank" @click.stop>
             <!-- creating a lot of Vue component is pretty slow, so we use a static SVG here -->
             <svg width="14" height="14" class="svg octicon-rss"><use href="#svg-symbol-octicon-rss"/></svg>
           </a>