MAINTAINERS: btrfs: fix git repo URL

The git repo listed for btrfs hasn't been updated in over a year.
List the current one instead.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

MAINTAINERS

@@ -3608,7 +3608,7 @@ M:	David Sterba <dsterba@suse.com>
 L:	linux-btrfs@vger.kernel.org
 W:	http://btrfs.wiki.kernel.org/
 Q:	http://patchwork.kernel.org/project/linux-btrfs/list/
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git
 S:	Maintained
 F:	Documentation/filesystems/btrfs.txt
 F:	fs/btrfs/