Update git submodules

* Update frameworks/support from branch 'androidx-main'
  to 21612e723f3c2de16c3885887763377c4ff8e262
  - Merge "Suppression for "DiffUtilActivity.java uses unchecked or unsafe operations"" into androidx-main
  - Suppression for "DiffUtilActivity.java uses unchecked or unsafe operations"
    
    Bug: 218323014
    
    Test: Download the gradle logs and validate them and see that they pass:
          /tmp/build_log_gc $ build_log_simplifier/build_log_simplifier.py --validate 8155046_androidx_incremental/gradle.1.log 8155046_androidx_incremental/gradle.2.log 8155046_androidx_incremental/gradle.log && echo ok
    
    Change-Id: Ie6c45ff0a5ddbe78b78c9cd353697a97cfd4b5cf