RDMA/mlx5: Delete never supported IPsec flow action

The IPSEC_REQUIRED_METADATA capability bit is never set, and can be
safely removed from the flow action flags.

Link: https://lore.kernel.org/r/697cd60bd5c9b6a004c449c1a41c2798fac844ff.1649232994.git.leonro@nvidia.com
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>