Remove volatile keyword from RepositoryEvent

We don't need this field to be volatile.  Events are delivered by
the same thread that created the RepositoryEvent object, and thus
any cross-thread operations would need to be handled by some other
type of synchronization in the listener, and that would protect
both the repository field and any other per-event data.

Change-Id: Iefe345959e1a2d4669709dbf82962bcc1b8913e3
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/events/RepositoryEvent.java

@@ -53,7 +53,7 @@ import org.eclipse.jgit.lib.Repository;
  *            type of listener this event dispatches to.
  */
 public abstract class RepositoryEvent<T extends RepositoryListener> {
-	private volatile Repository repository;
+	private Repository repository;
 
 	/**
 	 * Set the repository this event occurred on.