Fix analysis issues with Flutter v3.22

[Amir-P]

[Amir-P]

Thanks @Amir-P

We also need to update the CI

Thanks! Completely forgot about that. Now we have failing tests.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 70.00000% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 87.89%. Comparing base (2726f7d) to head (590b2d7).

Files	Patch %	Lines
packages/fleather/lib/src/widgets/checkbox.dart	69.38%	15 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #354      +/-   ##
==========================================
- Coverage   87.97%   87.89%   -0.08%     
==========================================
  Files          64       64              
  Lines       10380    10379       -1     
==========================================
- Hits         9132     9123       -9     
- Misses       1248     1256       +8     

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