Update git submodules

* Update plugins/replication from branch 'master'
  to 6a0e98744a5be2bd315aeb21193e313a3e9849ad
  - ReplicateRefUpdate: remove unnecessary factory method
    
    The only difference in the signature of the two create methods was in
    one parameter type: Set vs ImmutableSet. Since ImmutableSet is a subtype
    of Set we can remove the method with the ImmutableSet in the parameter
    type.
    
    Note that ImmutableSet.copyOf(Collection c) is smart enough to not
    create a copy of the passed collection when it is an ImmutableSet.
    
    Change-Id: Ifc689027d17ff7ebdcab36b3f70a0adaf7942f09
    
diff --git a/plugins/replication b/plugins/replication
index 5a51752..6a0e987 160000
--- a/plugins/replication
+++ b/plugins/replication
@@ -1 +1 @@
-Subproject commit 5a5175280743ce3da0e6267a1f04db55bbc7c779
+Subproject commit 6a0e98744a5be2bd315aeb21193e313a3e9849ad