GH Actions: run CodeQL only on cron-job, not on pull requests
GH Actions: run CodeQL only on cron-job, not on pull requests

Analysis takes more than 10 minutes, which is quite long to
run, so change it to only run on a cron job.

Also changing the cron to run on Thursdays instead of Fridays;
no need to worry about security issues during the Weekend.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

cpuguy83/cli,docker/cli,thaJeztah/cli,cpuguy83/cli,docker/cli,thaJeztah/cli