Fix alt text for readme badge (Mastodon -> Fediverse)

README.md

@@ -48,7 +48,7 @@
   </a>
   <br>
   <a rel="me" href="https://social.tchncs.de/@invidious">
-  <img alt="Mastodon: @invidious@social.tchncs.de" src="https://img.shields.io/badge/Fediverse-%40invidious%40social.tchncs.de-darkgreen">
+  <img alt="Fediverse: @invidious@social.tchncs.de" src="https://img.shields.io/badge/Fediverse-%40invidious%40social.tchncs.de-darkgreen">
   </a>
   <br>
   <a href="https://invidious.io/contact/">