Removing Travis CI

Dear Internals, Historically, we have been using Travis CI for our automated tests, but since 2021 June, travis-ci.org has ceased operations, and no longer runs any builds. There was an Internals discussion (https://externals.io/message/112709) to move to the successor, travis-ci.com, but I don't think we ever moved there. Quoting Nikita from that thread: > We haven't been using Travis as our primary CI for a while already. We use > AppVeyor for Windows testing and Azure Pipelines for everything else. The > only thing Travis is still used for is a daily cron job that tests PHP on > "exotic" architectures like aarch64 and s390x. Having those builds is a > nice to have, but not particularly critical. As far as I see, Travis does not run php-src builds anymore; neither on push, nor on cron. https://travis-ci.org/github/php/php-src leads to a page that says the project was moved to travis-ci.com, and the linked page (https://travis-ci.com/php/php-src) throws a 404. I think we have now fully moved to GitHub Actions (thanks to amazing efforts by Ilija) + Azure Pipelines + Appveyor + Circle CI, so perhaps it's time we remove all the Travis-related code from php-src? I'd gladly volunteer for it, if we reach a consensus to remove it. Thank you, Ayesh.