Update git submodules

* Update external/perfetto from branch 'master'
  to 396982cd6b1e89e84d081d3f7c8f29ea44a17c4c
  - Merge "trace_processor_shell: Clean up formatting of --help"
  - trace_processor_shell: Clean up formatting of --help
    
    Change-Id: Id3cf604c2ec351cadd02a599a5f7e207a3a1b6d3
1 file changed