Update git submodules

* Update external/boringssl from branch 'master'
  to cbbfa6936448f427dbe5b851463fc347a399983f
  - Merge "Drop deprecated libssl_static."
  - Drop deprecated libssl_static.
    
    There is only one remaining user on the internal master branch, and
    I'm dropping that one in a separate CL.
    
    Test: Treehugger
    Change-Id: I5375813b4c12502551914e84308ab7b33e31c9dc
    
1 file changed