From: Johannes Schindelin <johannes.schindelin@gmx.de>

This is a late amendment of 19ec39aab54 (ci: stop linking the `prove`
cache, 2022-07-10), fixing a bug that had been hidden so far.

The bug is that the `.prove` cache stores information about previous
`prove` runs (`save`) and uses them (`slow`, to run the tests in the
order from longer-running to shorter ones).

This bug can cause some surprising behavior: when the Prove cache
contains a reference to a test script, subsequent `prove` runs (with
`--state=slow`) will run the same test script again even if said script
is not specified on the `prove` command-line!

So far, this bug did not matter. Right until d8f416bbb87c (ci: run unit
tests in CI, 2023-11-09) it did not matter.

But starting with that commit, we run `prove` _twice_ in CI, and with
completely different sets of tests to run. Due to the bug, the second
invocation re-runs all of the tests that were already run as part of the
first invocation. This not only wastes build minutes, it also frequently
causes the `osx-*` jobs to fail because they already take a long time
and now are likely to run into a timeout.

The worst part about it is that there is actually no benefit to keep
running with `--state=slow,save`, ever since we decided no longer to
try to reuse the Prove cache between CI runs.

So let's just drop that Prove option and live happily ever after.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Submitted-As: https://lore.kernel.org/git/pull.1613.git.1699894837844.gitgitgadget@gmail.com