Bump actionpack, actionview, activesupport to 6.1

This is necessary for us to support Ruby 3.

It will resolve deprecation warnings such as:

/builds/gitlab-org/gitaly/ruby/vendor/bundle/ruby/2.7.0/gems/activesupport-6.0.3.6/lib/active_support/core_ext/time/calculations.rb:45: warning: Using the last argument as keyword parameters is deprecated

This will break under Ruby 3.

Updated via:

bundle update --conservative actionpack activesupport