Update git submodules

* Update prebuilts/androidx/external from branch 'androidx-master-dev'
  to d7a64e53ef247acf96252f5383d501037f4cd589
  - Merge "Remove dokka 1.4.10-dev-64 prebuilts" into androidx-master-dev
  - Remove dokka 1.4.10-dev-64 prebuilts
    
    Command used: git rm -r **/1.4.10-dev-64
    
    Bug: 168306746
    Test: Ran ./gradlew in dackka project
    Change-Id: I69c611e27e4edd22ff492eda8535b12a3a877922
    
1 file changed