Silence warnings on require for this test

The schema cache dump throws a warning and is supposed to. But we don't
want to see the warnings in test output, so silence them.

Author: eileencodes

railties/test/application/initializers/frameworks_test.rb

@@ -262,7 +262,9 @@ def show
       RUBY
 
       with_unhealthy_database do
-        require "#{app_path}/config/environment"
+        silence_warnings do
+          require "#{app_path}/config/environment"
+        end
 
         assert_not_nil ActiveRecord::Base.connection_pool.schema_cache