cam-app-example,test: Increase timeout_start_to_event for the streams

The CI spotted an intermittent issue where the timer is fired for
the timeout_start_to_event deadline, a similar issue was found for
the timeout_init_to_start and given the similar nature of the issue,
increasing the timeout_start_to_event is sensible and fixes the
error.

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>