Update git submodules

* Update docs/submodules/vnfsdk/model.git from branch 'master'
  to 6b71b531c0a3cd8dda66d0e43568673dfdaff9ae
  - Migrate vnfsdk-model docs
    
    Merging this will create
    https://onap-vnfsdk-model.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: Ifd688016f586aed584a20ecf8690f4c6caaf039a
    
1 file changed