Update git submodules

* Update frameworks/support from branch 'androidx-main'
  to 8f3482123c16075f2c64fccaa27fc46ff5cce7bc
  - Merge "Re-enable Gradle signature verification. Attempt #2" into androidx-main
  - Re-enable Gradle signature verification. Attempt #2
    
    Now with toml fixes!
    
    Test: ./gradlew bOS --dry-run
    Change-Id: I888372d181532ff55cf51475bf04ab039be2c773
    

* Update prebuilts/androidx/external from branch 'androidx-main'
  to f0a7a593106db375563155f714b9fa788e709f86
  - Merge "Add missing signatures of antlr4-master:4.7.2" into androidx-main
  - Add missing signatures of antlr4-master:4.7.2
    
    ./development/importMaven/import_maven_artifacts.py -n org.antlr:antlr4-master:4.7.2
    
    Test: ./gradlew bOS --dry-run
    Change-Id: Ia076eb4f476e0d82becd8c6fb81dab9a6351a18d