selftests/bpf: Mitigate sockmap_ktls disconnect_after_delete failure

"sockmap_ktls disconnect_after_delete" test has been failing on BPF CI
after recent merges from netdev:
* https://github.com/kernel-patches/bpf/actions/runs/14458537639
* https://github.com/kernel-patches/bpf/actions/runs/14457178732

It happens because disconnect has been disabled for TLS [1], and it
renders the test case invalid.

Removing all the test code creates a conflict between bpf and
bpf-next, so for now only remove the offending assert [2].

The test will be removed later on bpf-next.

[1] https://lore.kernel.org/netdev/[e-mail]/
[2] https://lore.kernel.org/bpf/[e-mail]/

Signed-off-by: Ihor Solodrai <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Reviewed-by: Jiayuan Chen <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/prog_tests/sockmap_ktls.c

···
 		goto close_cli;
 
 	err = disconnect(cli);
-	ASSERT_OK(err, "disconnect");
 
 close_cli:
 	close(cli);