Disable scheduled jobs for forks

[andyw8]

To prevent unwanted runs, e.g. https://github.com/andyw8/irb/actions/runs/13265307995

[ima1zumi]

I have a use case where I want to check the CI results on my forked repository, so I’d like to disable only the scheduled job. How about this?

Suggested change

	if: github.repository == 'ruby/irb'
	if: github.event_name == 'schedule' && github.repository != 'ruby/irb'

[tompng]

if: github.repository == 'ruby/irb' || github.event_name != 'schedule'
Examples in other repositories in ruby org
https://github.com/search?q=org%3Aruby%20github.event_name%20%22%27schedule%27%22&type=code

I wish GitHub have a configuration of enabling/disabling scheduled jobs, not the whole workflow.

[tompng]

This if: (and if: in vterm-yamatanooroti job) is not needed because these jobs depend on ruby-versions.
Maybe lint and debug-test can have needs: ruby-versions so that we don't need to write many if: with the same condition. (I'd be happy if there is a better idea)

[andyw8]

Updated with @tompng's feedback.