LfsStore: Make inner class AppServer static

FindBugs reports:

  This class is an inner class, but does not use its embedded reference
  to the object which created it. This reference makes the instances
  of the class larger, and may keep the reference to the creator object
  alive longer than necessary. If possible, the class should be made
  static.

Change-Id: I245e44678166176de0cfb275e22ddd159f88e0bd
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/LfsStore.java

@@ -82,7 +82,7 @@ class LfsStore extends TextBuiltin {
 	/**
 	 * Tiny web application server for testing
 	 */
-	class AppServer {
+	static class AppServer {
 
 		private final Server server;