Fix typo in db.rake (#16126)

occured -> occurred

lib/tasks/db.rake

@@ -22,7 +22,7 @@ namespace :db do
       unless %w(C POSIX).include?(ActiveRecord::Base.connection.select_one('SELECT datcollate FROM pg_database WHERE datname = current_database();')['datcollate'])
         warn <<~WARNING
           Your database collation is susceptible to index corruption.
-            (This warning does not indicate that index corruption has occured and can be ignored)
+            (This warning does not indicate that index corruption has occurred and can be ignored)
             (To learn more, visit: https://docs.joinmastodon.org/admin/troubleshooting/index-corruption/)
         WARNING
       end