Update git submodules

* Update docs/submodules/usecase-ui.git from branch 'master'
  to 88f8607f42193606135191083b38b164991befa0
  - Merge "Migrate usecase-ui docs"
  - Migrate usecase-ui docs
    
    Merging this will create
    https://onap-usecase-ui.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: I2c2993ac3d0426b7bf81e16e3bf8ee61b6d00dff
    
1 file changed