[geolocator_android] Resolves ./gradlew build issue

[arrrrny]

When I ran ./gradlew clean
./gradlew build

I was getting below error. This PR fixes the build issue.

> Task :geolocator_android:lintDebug FAILED
Lint found 1 errors, 6 warnings. First failure:

/Users/altezza/.pub-cache/hosted/pub.dev/geolocator_android-4.6.1/android/src/main/java/com/baseflow/geolocator/location/BackgroundNotification.java:100: Error: Missing permissions required by NotificationManagerCompat.notify: android.permission.POST_NOTIFICATIONS [MissingPermission]
            notificationManager.notify(notificationId, builder.build()

Pre-launch Checklist

• I made sure the project builds.
• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I updated pubspec.yaml with an appropriate new version according to the [pub versioning philosophy], or this PR is does not need version changes.
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I rebased onto main.
• I added new tests to check the change I am making, or this PR does not need tests.
• I made sure all existing and new tests are passing.
• I ran dart format . and committed any changes.
• I ran flutter analyze and fixed any errors.