chore: Remove test and flutter_test dependencies

[st-pasha]

Description

Similar to #1361, dependencies test and flutter_test are unnecessary, since they are part of the Flutter SDK.

Removing these dependencies is beneficial, because occasionally they create version mismatch with error messages like

Because test >=1.19.4 <1.20.0 depends on test_api 0.4.8 and test >=1.19.3 <1.19.4 depends on test_api 0.4.7, test >=1.19.3 <1.20.0 requires test_api 0.4.7 or 0.4.8.
And because test >=1.20.0 depends on test_api 0.4.9, test >=1.19.3 requires test_api 0.4.7 or 0.4.8 or 0.4.9.
Because every version of flame_test depends on flutter_test from sdk which depends on test_api 0.4.3, every version of flame_test requires test_api 0.4.3.
Thus, flame_test is incompatible with test >=1.19.3.
So, because flame depends on both test ^1.19.3 and flame_test ^1.1.0, version solving failed.

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• (NA) I have updated/added tests for ALL new/updated/fixed functionality.
• (NA) I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• (NA) I have updated/added relevant examples in examples.

Breaking Change

• No, this is not a breaking change.