RSS icon fixes (#24476)

Fix regression from https://github.com/go-gitea/gitea/pull/24471 where
CSS rules for `.icon.grey` were removed which were in use by the RSS
icons.

Gave them their own class instead, removed a wrapper and also fixed
vertical alignment on them. Additionally, did a few related fixes on the
org header for alignment.

Fixes: https://github.com/go-gitea/gitea/issues/24584

<img width="196" alt="Screenshot 2023-05-01 at 22 39 40"
src="https://user-images.githubusercontent.com/115237/235528228-959e2385-c1d2-4d5c-baec-e3784d459653.png">
<img width="216" alt="Screenshot 2023-05-01 at 22 44 20"
src="https://user-images.githubusercontent.com/115237/235528231-95cbff86-5672-48eb-b214-8bdcefa1612c.png">
<img width="120" alt="Screenshot 2023-05-01 at 22 56 36"
src="https://user-images.githubusercontent.com/115237/235529844-b94ab554-3259-4d0c-b040-82aed7d1a111.png">


<img width="372" alt="Screenshot 2023-05-01 at 22 54 25"
src="https://user-images.githubusercontent.com/115237/235529744-1a9c201b-5692-4122-9765-2f201a322a9e.png">
<img width="477" alt="Screenshot 2023-05-01 at 22 55 28"
src="https://user-images.githubusercontent.com/115237/235529748-62188554-9927-42ef-bc94-7052bce266e2.png">

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/components/RepoBranchTagSelector.vue

@@ -39,7 +39,7 @@
       <div class="scrolling menu" ref="scrollContainer">
         <div v-for="(item, index) in filteredItems" :key="item.name" class="item" :class="{selected: item.selected, active: active === index}" @click="selectItem(item)" :ref="'listItem' + index">
           {{ item.name }}
-          <a v-if="enableFeed && mode === 'branches'" role="button" class="ui compact muted right" :href="rssURLPrefix + item.url" target="_blank" @click.stop>
+          <a v-if="enableFeed && mode === 'branches'" role="button" class="ui compact right muted" :href="rssURLPrefix + item.url" target="_blank" @click.stop>
             <svg-icon name="octicon-rss" :size="14"/>
           </a>
         </div>