Update git submodules

* Update frameworks/support from branch 'androidx-main'
  to 313848aa39dc9606ea95bb9b6f852c007d8c9f69
  - Merge "Update GSON to 2.9.0" into androidx-main
  - Update GSON to 2.9.0
    
    Addresses the security vulnerability: https://security.snyk.io/vuln/SNYK-JAVA-COMGOOGLECODEGSON-1730327
    
    Test: ./gradlew bOS
    Bug: 205495360
    Change-Id: I5756bf04a6ff6782440d7e6ea89e120e7006c3dc
    

* Update prebuilts/androidx/external from branch 'androidx-main'
  to 3766fb25f3c3bb50916706d36d83a3c4560b099d
  - Merge "Import GSON 2.9.0" into androidx-main
  - Import GSON 2.9.0
    
    Via: import_maven_artifacts.py -n com.google.code.gson:gson:2.9.0
    Test: n/a
    Change-Id: I1a50f4de0b215a2a434c347d1cefdedd660a250c