Update notes for submitted changes

* GC.prune(Set<ObjectId>): return early if objects directory is empty

a1/1bb03127b9ab193c956589381c496429f82d87

@@ -0,0 +1,7 @@
+Verified+1: Hudson CI
+Code-Review+2: Christian Halstrick <christian.halstrick@sap.com>
+Submitted-by: Christian Halstrick <christian.halstrick@sap.com>
+Submitted-at: Thu, 02 Feb 2017 03:05:58 -0500
+Reviewed-on: https://git.eclipse.org/r/89823
+Project: jgit/jgit
+Branch: refs/heads/stable-4.6