Update git submodules

* Update docs/submodules/usecase-ui.git from branch 'master'
  to c0df9473c17c1c9b9e98c287e56a17de0d14796f
  - Merge "Update css file name in conf.py"
  - Update css file name in conf.py
    
    ribbon.css is the correct name of the css file.
    
    Issue-ID: CIMAN-376
    Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
    Change-Id: I472791266fb1799f76b34273ccb31b95cbbdc132
    
1 file changed