Update git submodules

* Update docs/submodules/usecase-ui.git from branch 'master'
  to 4ad574c3b6d6bc28ed83fa222f3a8a74c951c346
  - docs: modify 5g user guide doc
    
    Change-Id: I77d878530a8ff4a98c690259341e0286a2b5f331
    Issue-ID: USECASEUI-428
    Signed-off-by: cyuamber <xuranyjy@chinamobile.com>
    
diff --git a/docs/submodules/usecase-ui.git b/docs/submodules/usecase-ui.git
index da22de9..4ad574c 160000
--- a/docs/submodules/usecase-ui.git
+++ b/docs/submodules/usecase-ui.git
@@ -1 +1 @@
-Subproject commit da22de958013506c0a5b2ff6d055425a8c1fae3c
+Subproject commit 4ad574c3b6d6bc28ed83fa222f3a8a74c951c346