Revert "Add Ruby 3 to the CI matrix"
Revert "Add Ruby 3 to the CI matrix"

Seems we're blocked by https://github.com/rspec/rspec-mocks/pull/1394

This reverts commit da4ff3e3cb9fe38403d0e40039a9189d77e6547f.

DNNX/chewy,toptal/chewy