Revert "DEV: upgrade to Rails 6.0.3"

This was causing issues during multisite:migrate

https://meta.discourse.org/t/multisite-migrate-broken-since-rails-6-0-3-update/150691

This reverts commit 136a545653.

Gemfile

@@ -18,13 +18,13 @@ else
   # this allows us to include the bits of rails we use without pieces we do not.
   #
   # To issue a rails update bump the version number here
-  gem 'actionmailer', '6.0.3'
-  gem 'actionpack', '6.0.3'
-  gem 'actionview', '6.0.3'
-  gem 'activemodel', '6.0.3'
-  gem 'activerecord', '6.0.3'
-  gem 'activesupport', '6.0.3'
-  gem 'railties', '6.0.3'
+  gem 'actionmailer', '6.0.2.2'
+  gem 'actionpack', '6.0.2.2'
+  gem 'actionview', '6.0.2.2'
+  gem 'activemodel', '6.0.2.2'
+  gem 'activerecord', '6.0.2.2'
+  gem 'activesupport', '6.0.2.2'
+  gem 'railties', '6.0.2.2'
   gem 'sprockets-rails'
 end