Remove custom font for golden tests in preference for FlutterTest font

[kawaijoe]

Golden tests with custom fonts can be flaky as fonts are rendered differently based on the platform/flutter version. It could be worth considering migrating to the default FlutterTest font to ensure the tests are rendered consistently.

Additional resources

• https://api.flutter.dev/flutter/flutter_test/matchesGoldenFile.html
• https://docs.flutter.dev/release/breaking-changes/rendering-changes

[Pante]

We probably should split the migration equally across multiple people. Having a single person do it is going to be soul crushing.

On another note, this should only proceed after we thoroughly investigated the layout test library.

[Pante]

We're currently evaluating an alternative where flutter golden tests are ran inside a ubuntu docker image. This will allow us to eliminate flakiness while retaining the benefits of using actual fonts.