Target ruby 3 with rubocop

[ellnix]

Rubocop's config was still enforcing ruby 2 code style. This is just a step that was missing in #367.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.90%. Comparing base (c4abc60) to head (451f931).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #370 +/- ## ======================================= Coverage 88.90% 88.90% ======================================= Files 13 13 Lines 757 757 ======================================= Hits 673 673 Misses 84 84 ```

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[curquiza]

@ellnix sorry can you fix the git conflicts? 🙈

[ellnix]

@ellnix sorry can you fix the git conflicts? 🙈

Apologies for ghosting for so long, fixed the conflict (it was an edit to a file that has since been deleted)