fix(android): add missing namespace to support AGP 7.0+

[yen-kadokawa]

Description of the change

Add missing namespace declaration in android/build.gradle to support Android Gradle Plugin (AGP) 7.0 and above.

Could not create an instance of type com.android.build.api.variant.impl.LibraryVariantBuilderImpl.
> Namespace not specified. Specify a namespace in the module's build file.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Maintenance
• New release

Related issues

Bug: Build fails on AGP 7.0+ due to missing namespace

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• "Ready for review" label attached to the PR and reviewers assigned
• Issue from task tracker has a link to this pull request
• Changes have been reviewed by at least one other engineer

[matux]

Thank you!