Update git submodules

* Update docs/submodules/usecase-ui.git from branch 'master'
  to b7d48cb394ab3669a360ccc1672bdc196982abfa
  - Merge "Service Topology Changes"
  - Service Topology Changes
    
    Issue-ID: USECASEUI-419
    
    Signed-off-by: phani.y <yellela.nagaphanindra@huawei.com>
    Change-Id: I4f2d8a5a6309de92acd9384d499a285306036ebf
    
1 file changed