Bluetooth: Audio: Remove !found dbg log in codec.c

It is a common occurance that a specific type is not
found in the codec configuration, and the main way of
knowing that is by calling the function.

The debug log does not help debug anything (as it does also
return a specific error code), but rather just clutters up
the log if enabled.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>