Update git submodules

* Update docs/submodules/usecase-ui.git from branch 'master'
  to f23ed2484b1a51ed11e6d0b104f3c31f63ab8b45
  - change for the slice mgmt UI
    
    Issue-ID: USECASEUI-387
    
    Signed-off-by: seshukm <seshu.kumar.m@huawei.com>
    Change-Id: I57de2b33bc10b2c60c9c7054e4e3a35580bada79
    
1 file changed