Bluetooth: Host: Remove conn param update checks

The rationale behind that change is that the Application can use the
`bt_conn_le_param_update()` API to signal the controller to reschedule
the link.

Even if the new connection params are within the old ones, the
controller would be free to choose an e.g. smaller interval. The host
API should not prevent this usage.

Fixes https://github.com/zephyrproject-rtos/zephyr/issues/74292



Co-authored-by: Knut Eldhuset <knut.eldhuset@nordicsemi.no>
Signed-off-by: Jonathan Rico <jonathan.rico@nordicsemi.no>