Update CI configuration

[waiting-for-dev]

Summary

Run different Solidus versions on different jobs for better error handling.

We're now explicitly providing the ruby version to the executor while using a matrix configuration for better extensibility.

We're now running the linter on Ruby v3.0, as that's the minimal requirement for Solidus master. As a consequence, we disable the cop for following the gemspec version.

Checklist

Check out our PR guidelines for more details.

The following are mandatory for all PRs:

• [x] I have written a thorough PR description.
• [x] I have kept my commits small and atomic.
• [x] I have used clear, explanatory commit messages.

The following are not always needed:

• 📖 I have updated the README to account for my changes.
• 📑 I have documented new code with YARD.
• 🛣️ I have opened a PR to update the guides.
• ✅ I have added automated tests to cover my changes.
• 📸 I have attached screenshots to demo visual changes.

[waiting-for-dev]

CI should be fine once we release a new version of solidus_dev_support with https://github.com/solidusio/solidus_dev_support/pull/205

[kennyadsl]

@waiting-for-dev I think we need to remove this line: https://github.com/solidusio/solidus_auth_devise/blob/97342f783fe2ce131192187c31b0abe1c892b9de/spec/support/spree.rb#L3. It's not needed anymore, now that we have https://github.com/solidusio/solidus_auth_devise/blob/97342f783fe2ce131192187c31b0abe1c892b9de/spec/spec_helper.rb#L24.

[waiting-for-dev]

@waiting-for-dev I think we need to remove this line:

https://github.com/solidusio/solidus_auth_devise/blob/97342f783fe2ce131192187c31b0abe1c892b9de/spec/support/spree.rb#L3

. It's not needed anymore, now that we have https://github.com/solidusio/solidus_auth_devise/blob/97342f783fe2ce131192187c31b0abe1c892b9de/spec/spec_helper.rb#L24

.

Good call. Changed!