Fix CommunitySelector format

[micahmo]

Pull Request Description

This PR fixes an issue where the CommunitySelector would not respect the selected community full name syntax. It was using getLemmyCommunity which is more for resolving and verifying the identity of a community to a common syntax with which we can navigate. Instead it should have used generateCommunityFullName which is purely a textual transformation. This change should also slightly reduce the overhead of calling getLemmyCommunity which was async.

Issue Being Fixed

Issue Number: N/A

Screenshots / Recordings

Checklist

• Did you update CHANGELOG.md?
• Did you use localized strings where applicable?
• Did you add semanticLabels where applicable for accessibility?

[hjiangsu]

LGTM!