Update git submodules

* Update plugins/reviewnotes from branch 'stable-2.15'
  to 52d66d97f7c87a18c50840ab453ca84026b90738
  - Return early for branches for which we do not want to create review notes
    
    Change-Id: I6de283673a1cda19667b3694c68d02e47e516106
    Signed-off-by: Edwin Kempin <ekempin@google.com>
    (cherry picked from commit 4cea41a51ff7ce98bc18e4c01577f99a93931562)
    
diff --git a/plugins/reviewnotes b/plugins/reviewnotes
index eb09af3..52d66d9 160000
--- a/plugins/reviewnotes
+++ b/plugins/reviewnotes
@@ -1 +1 @@
-Subproject commit eb09af38459c25ba3056b4f4ee0ef181f42915b2
+Subproject commit 52d66d97f7c87a18c50840ab453ca84026b90738