Fix CI (as it installs RuboCop 1.45.1 and fails)

[karreiro]

The CI no longer uses RuboCop 1.44.1 (instead it uses 1.45.1). So, it's failing with this error now:

Inspecting 136 files
.....................................................................W..................................................................

Offenses:

performance/shopify/database.rb:54:3: W: Lint/Debugger: Remove debugger entry point p(Database.tables['collections']['frontpage'].keys).
  p(Database.tables['collections']['frontpage'].keys)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

136 files inspected, 1 offense detected

Also, I can open a following PR to remove rubocop from the Gemfile and update rubocop-shopify to `2.12.0' (still, it will require broader changes).

[dylanahsmith]

It makes sense to be more specific with the rubocop version to avoid having CI silently break by inheriting these non-backwards compatible changes. However, I think we could also remove that offending code, since it does seem to be for debugging.

[karreiro]

Thank you for the review, @dylanahsmith! I've removed the debugging snippet on this PR and merged it.

Also, following this work, I've opened #1687 updating rubocop-shopify.