ci: bsim tests: Trigger on any change on tests/bluetooth

As time passes we are adding more babblesim tests which depend on code/
tests from tests/bluetooth just like we have many based on samples from
samples/bluetooth.
Let's also trigger the Babblesim CI job when anything changes in
tests/bluetooth, instead of trying to pinpoint the specific folders we
use, as otherwise every now and then we have coverage holes and issues
are introduced in main.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>