Remove backported code from WP 6.0 compat layer

[ockham]

Now that WordPress 6.1 has been released, we should remove the back-compat code for WordPress 6.0 (in lib/compat/wordpress-6.0/) from Gutenberg. This is because Gutenberg supports the current and previous versions of WordPress (i.e 6.1 and 6.0); the code in lib/compat/wordpress-6.1/ is needed to allow it to work on a WP 6.0 installation (which lacks some code that is in 6.1). (OTOH, the lib/compat/wordpress-6.0/ dir is no longer needed, as it provides backwards compatibility for WP 5.9 and older; but those versions are no longer supported by Gutenberg.)

We should also look out for tests for that code in phpunit, make sure that those tests have been carried over to wordpress-develop (and add them there if they haven't), and remove them.

We might need to exercise a bit more care when removing code in lib/block-supports; I'm not entirely sure how that (unversioned) compat layer is applied to Gutenberg.

cc/ @c4rl0sbr4v0 @ramonjd @oandregal @scruffian in case y'all wanna help with this 😊

[ramonjd]

cc/ @c4rl0sbr4v0 @ramonjd @oandregal @scruffian in case y'all wanna help with this

You bet. I started with typography a while back already: #43928 Need to dust it off.

Will be out of action next week, but I'll put this issue on a list to remind my brain.

[Mamaduka]

We cannot remove code from the WP 6.1 compat layer, only from 6.0. The plugin still has to support WP 6.0.

[ockham]

We cannot remove code from the WP 6.1 compat layer, only from 6.0. The plugin still has to support WP 6.0.

Of course 🤦‍♂️ Thank you for pointing that out! I'll change the issue title and contents 😅

[ockham]

Closed by #46102.