Remove Travis and update Unit test GH action

[imath]

Travis-ci.org is now ended. Builds are no more run there, migrating to Travis-ci.com is required. My experience with 2 of my open source plugins with .com wasn't great: after a bunch of builds the service stopped asking me to pay 69$ per month. But I must say that 4 months after I contacted their support team arguing my repository were open source ones they finally replied saying they gave me free credits for their services. I haven't checked if this was true since I removed my Travis-CI.com personal account & the Travis CI authorization on my GitHub account after waiting for a reply for 2 months.

Now that we have a unit tests GH action, doing this migration might not be needed. GitHub is directly free, you don't need to request free credits and wait 4 months or less to get them.

I'm personally more in favor of improving our GH actions (adding new ones) than migrating to Travis-ci.com. That's why the patch is removing the Travis config and tasks. @johnjamesjacoby what's your opinion about it?

About our unit tests GH Action, now that WordPress has created the 5.8 branch, we need to update it (this is also in the attached patch).

[johnjamesjacoby]

GitHub actions seems like the way to go. 👍

[imath]

In 12992:

Remove Travis & raise min. WP version in Unit tests GH action

Bye & thanks for your services Travis-CI.org, we decided migrating to .com was not for us and preferred to switch to GitHub actions instead.

As we're starting merging Widget Blocks from our BP Blocks feature as a plugin to Core, let's update the min. tested WP version to 5.8 to limit the risks of mistakes.

props johnjamesjacoby

Fixes #8501

[imath]

It looks like wp-env is using WP tags instead of WP branches. The 5.8 tag is not released yet, which explains why the tests are failing. I'm going to edit back the GH action so that it uses 5.7 until 5.8 is released (~ July 20).

We'll need to update it again soon ;)

[imath]

In 12993:

Decrease unit tests GH action tested WP min. version to 5.7

wp-env is using WP tags instead of WP branches, as the 5.8 tag has not been released yet, we need to wait for it to avoid GitHub fetching errors.

See #8501

[imath]

Let's try to progress on it during 10.0.0 dev cycle.

[imath]

In 13030:

PHPUnit tests: increase WP min. version to test to 5.8

Fixes #8501