ci: re-enable tests using the beta channel

[amondnet]

Describe the changes proposed in this Pull Request.

If the PR fixes a specific issue, reference the issue with Fixes #.

I removed tests using the beta channel in #907. This PR reverts it.

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Pull Request Checklist

• If the changes are being made to code, ensure the version in pubspec.yaml is updated.
• Increment the major/minor/patch/patch-count, depending on the complexity of change
• Add the necessary unit tests to ensure the coverage does not drop
• Update the Changelog to include all changes made in this PR, organized by version
• Run the melos run set_version command from the root directory
• Include the necessary reviewers for the PR
• Update the docs if there are any API changes or additions to functionality

[netlify]

✅ Deploy Preview for mobx canceled.

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🔨 Latest commit	b28aeaa
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (41f55df) 99.01% compared to head (0b8418d) 99.01%.
Report is 1 commits behind head on main.

❗ Current head 0b8418d differs from pull request most recent head b28aeaa. Consider uploading reports for the commit b28aeaa to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #980   +/-   ##
=======================================
  Coverage   99.01%   99.01%           
=======================================
  Files          57       57           
  Lines        2024     2024           
=======================================
  Hits         2004     2004           
  Misses         20       20           

Flag	Coverage Δ
flutter_mobx	100.00% <ø> (ø)
mobx	98.56% <ø> (ø)
mobx_codegen	100.00% <ø> (ø)
mobx_lint	∅ <ø> (∅)

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