Update git submodules

* Update docs/submodules/music.git from branch 'master'
  to 9399b2eed91169c719acd9a966b4c5ed560897a8
  - Migrate music docs
    
    Merging this will create
    https://onap-music.readthedocs.io
    This build will run in parallel
    to the current docs generation method
    until we are ready to cut over.
    
    Issue-ID: CIMAN-364
    Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
    Change-Id: Icbac29b0d981370c9e0db7937b2acef97387ed2e
    
1 file changed