s4:pysmb: Add error log that the s4 bindings are deprecated

s4:pysmb: Add error log that the s4 bindings are deprecated

We plan to delete the s4 SMB Python bindings in the next Samba release
after v4.10, but first give external consumers a heads-up, just in case
they are currently using the s4 bindings.

Note the auth_log tests still use the s4 bindings, but all user-facing
tools should now be updated to use the s3 bindings.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13676

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Jeremy Allison <jra@samba.org>