bump buildToolsVersion to 30.0.2 (#31627)

Summary:
Bump buildToolsVersion to 30.0.2, default version of Android Gradle Plugin 4.2.0. Fixes parity with https://github.com/facebook/react-native/pull/31593

## Changelog

[Android] [Changed] - Bump buildToolsVersion to 30.0.2,

Pull Request resolved: https://github.com/facebook/react-native/pull/31627

Test Plan: Newly created projects will use build tools 30.0.2 to build dependencies.

Reviewed By: yungsters

Differential Revision: D28833598

Pulled By: ShikaSD

fbshipit-source-id: 009472d27ea7103bdc7e5a6a941ab529d982f2da