Remove dead isBinary method from DiffFormatter

This method always returns false and is private so it cannot be
overridden at runtime by a subclass. Drop the method and the branch
that can never be taken.

Change-Id: I4d3edbf469c6739dca191e62ea580bdb534b67a4

org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffFormatter.java

 		if (entry.getMode(side).getObjectType() != Constants.OBJ_BLOB)
 			return EMPTY;
 
-		if (isBinary())
-			return BINARY;
-
 		AbbreviatedObjectId id = entry.getId(side);
 		if (!id.isComplete()) {
 			Collection<ObjectId> ids = reader.resolve(id);
 		}
 	}
 
-	private boolean isBinary() {
-		return false;
-	}
-
 	/**
 	 * Output the first header line
 	 *