Use silence instead of quietly to silence the CheckPending middleware.

`Kernel.quietly` silences `STDOUT` and `STDERR`, which is useless if
the logger is writing to a file, while `AS::Logger#silence` swaps the
logger level to `ERROR`.

Related to #8820 and #8052.

activerecord/lib/active_record/migration.rb

@@ -342,7 +342,7 @@ module ActiveRecord
       end
 
       def call(env)
-        ActiveRecord::Base.logger.quietly do
+        ActiveRecord::Base.logger.silence do
           ActiveRecord::Migration.check_pending!
         end
         @app.call(env)