Use HTTPS MDPI link and increase urlchecker timeout.

5 jobs for master in 18 minutes and 37 seconds (queued for 3 seconds)
Name Stage Failure
test_urls Test
No urls found.

🤔 Uh oh... The following urls did not pass:
make: *** [Makefile:66: urlcheck] Error 1
Cleaning up file based variables
ERROR: Job failed: exit code 1