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