Update git submodules

* Update plugins/plugin-manager from branch 'master'
  to ba74d4969462c2592bcf97868dd76c33041d47b2
  - Filter out JsonNull values in artifacts meta-data fields
    
    Consider fields having a null value as inexistent, so that
    they are automatically filtered out in the list of plugins
    displayed by the plugin manager.
    
    Bug: Issue 290658426
    Change-Id: I45d8a613a0ced6610d226069a8f1a5212345414e
    
diff --git a/plugins/plugin-manager b/plugins/plugin-manager
index dbd6820..ba74d49 160000
--- a/plugins/plugin-manager
+++ b/plugins/plugin-manager
@@ -1 +1 @@
-Subproject commit dbd68200d867513e2c0449798476e275aaf08cfd
+Subproject commit ba74d4969462c2592bcf97868dd76c33041d47b2