Pin active_material to earlier version

[alexeyschepin]

Motivation / Background

v1 version of activeadmin_addons has a dependency on active_material gem. active_material gem had recently a new release that relies on ruby 3.1 built-in methods without setting it in required_ruby_version. That leads the app running on ruby 3.0 to crash.

Detail

It can be fixed if a dependency on active_material had more specific range like (~> 1.5) or (~> 1.5.2)

Additional information

I've also sent a PR to active_material https://github.com/dkniffin/active_material/pull/100

Checklist

Before submitting the PR make sure the following are checked:

• [x] This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• [x] Commit message has a concise description of what changed and why.
• [N/A] Tests are added or updated if you fix a bug or add a feature.
• [N/A] Documentation has been added or updated if you add a feature or modify an existing one.
• [N/A] CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature (under the "Unreleased" heading if this is not a version change).
• [x] My changes don't introduce any linter rule violations.

[rjherrera]

hey, thanks for the PR, looks good to me