Cleanup unused i18n strings (#23426)

* Remove partial 422/500 error translations

* Add missing siblings for i18n unused warnings

* Enable i18n unused string checking for all locales

config/locales/tt.yml

@@ -136,9 +136,7 @@ tt:
     '404': The page you are looking for isn't here.
     '406': This page is not available in the requested format.
     '410': The page you were looking for doesn't exist here anymore.
-    '422': 
     '429': Too many requests
-    '500': 
     '503': The page could not be served due to a temporary server failure.
   exports:
     archive_takeout:
@@ -183,6 +181,8 @@ tt:
     truncate: "…"
   preferences:
     other: Башка
+    posting_defaults: Posting defaults
+    public_timelines: Public timelines
   relationships:
     following: Язылгансыз
   sessions: