... which is expected to be released this Thursday.
* Builds against PHP 8.5 are no longer allowed to fail.
* Update PHP version on which code coverage is run (high should now be 8.5).
* Add _allowed to fail_ build against PHP 8.6.
* Update the README.
Note: for some jobs I use "nightly" for the "next" PHP version, for some `8.6`. While it may appear there is no difference and this is true for the better part of the year, there is a difference for about two months.
To illustrate, consider PHP 8.5:
* PHP "nightly" refers to the PHP `master` branch, so was PHP 8.5 until the PHP 8.5 was branched off when the first RC was cut in September.
* As of that moment, "nightly" basically became PHP 8.6, so to test against PHP 8.5, one would need to explicitly request `8.5`.
* As of the release of PHP 8.5, it is expected for "nightly" to be PHP 8.6, so the difference is moot again.
For that reason, the unit test workflow uses the explicit `8.6` version for PHP "next".
f5cc77c68a