Fix ./gradlew lint warnings

[arriolac]

Steps to reproduce

1. Run ./gradlew lint and address all warnings presented (you can see warnings reported in here: https://github.com/googlemaps/android-maps-ktx/actions/runs/109748915).

Code example

./gradlew lint

Stack trace

w: /Users/chrisarriola/workspace/android-maps-ktx/maps-v3-ktx/src/main/java/com/google/maps/android/ktx/MapFragment.kt: (25, 2): This class can only be used with the compiler argument '-Xopt-in=kotlin.RequiresOptIn'

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This issue has been automatically marked as stale because it has not had recent activity. Please comment here if it is still valid so that we can reprioritize. Thank you!

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Please comment here if it is still valid so that we can reprioritize. Thank you!

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Please comment here if it is still valid so that we can reprioritize. Thank you!

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Please comment here if it is still valid so that we can reprioritize. Thank you!