chore: ignore deprecated use of 'ButtonBarThemeData' and fix unit tests

[cyrilcolinet]

Description

Ignore the use of ButtonBarThemeData and fix some unit tests (according to #208 PR)

Checklist

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• I read the Code Style Guide and followed the process outlined there for submitting PRs.
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (flutter analyze or dart analyze) does not report any problems on my PR.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy.
• I updated CHANGELOG.md to add a description of the change.
• I am authorized to release this code under the MIT License and agree to do so

UI Change

Does your PR affect any UI screens?

• Yes, the relevant screens are included below.
• No, there are no UI impacts with this PR.