Linux 6.6 compat: META

Update the META file to reflect compatibility with the 6.6 kernel.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Umer Saleem <usaleem@ixsystems.com>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #15520