NoteMapMerger: remove unnecessary cast

Change-Id: I3be4963f506529bbadc5b6dfc0b625ee85effc1f

org.eclipse.jgit/src/org/eclipse/jgit/notes/NoteMapMerger.java

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/notes/NoteMapMerger.java b/org.eclipse.jgit/src/org/eclipse/jgit/notes/NoteMapMerger.java
index 79ceb13..30512c1 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/notes/NoteMapMerger.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/notes/NoteMapMerger.java
@@ -199,7 +199,7 @@ private void addIfNotNull(FanoutBucket b, int cell, NoteBucket child)
 		if (child == null)
 			return;
 		if (child instanceof InMemoryNoteBucket)
-			b.setBucket(cell, ((InMemoryNoteBucket) child).writeTree(inserter));
+			b.setBucket(cell, child.writeTree(inserter));
 		else
 			b.setBucket(cell, child.getTreeId());
 	}