tests: Bluetooth: llcp: cte_req: remove invalid rsp test

There is a test that verifies a behavior of CTE request control
procedure if receives LL_UNKNOWN_RSP. The expected behavior
is to terminate connection if that is response handling is
not implemented by a command. Other unexpected responses are
treated as new remote control procedures.

The CTE request has implemented handling of LL_UNKNOWN_RSP,
hence this particular test is no longer valid.

There is still open question how to handle other unexpected
reposne PDUs while waiting for LL_CTE_RSP. That is not defined
by BT 5.3. Core specification and not decided by community.

The test is removed to because it fails and blocks CI.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>