Remove support for travis-ci

[andrewnicols]

It's been a few years since we stopped using Travis CI in Moodle core, but we have continued to provide a travis configuration here and test it.

Travis is rarely used these days, and we currently pay to maintain it. I'd like to propose that we remove official support for it, and stop testing with it.

[kabalin]

I support this idea @andrewnicols, I assume it is rarely used, we don't have stats though. I am thinking to remove test, but leave config template and docs in place, may be move it to "other CI tools" where we can add Gitlab example, but with no commitment to keep it up to date or support. We should also change documentation to imply that GHA is the only supported workflow (also given plans to add custom action #53).

[stronk7]

Adding my 2 cents… what I basically would do is:

• Declare it deprecated now (new release) and announce it in the 4.x series (assuming that it’s still working).
• Take on version 5, that was almost working (surely there is stuff in 4.x to rebase there, I’ve not been following). Remove Travis support there and release 5.0.

That’s my very overall opinion.

[kabalin]

Deprecation notes have been added to 4.5.8 release.