fix: exclude specific folders from coverage

[stact]

Description Hi team, we are not able exclude folders from coverage, I don't know if it's a bug, or For instance we have generated folder that include our localization

`very_good test --coverage --exclude-coverage "lib/l10n/**"``

Steps To Reproduce

1. On your project folder create dummy folder with some dart files
2. Open a terminal
3. "cd" to your flutter project folder
4. Launch the coverage very_good test --coverage --exclude-coverage "lib/l10n/**"
5. See the results of the coverage (using vscode flutter coverage extension)

Expected Behavior The folder excluded must be ignored for coverage

Screenshots

Additional Context Tried also to ignore files directly it's not working too