[CI] Stale issues getting closed again by bot

[marcalff]

See #2165

At some point in the past, automatically closing stale issues was disabled in CI (#1453),
but it seems this change got lost after upgrading actions/stale in stale.yml to newer versions.

Automatically closing stale issues is not desirable, the issue can be relevant and valid, even if not worked on.

A typical example of old and valid issues that are worth keeping is #873, it would never have been found and fixed if automatically closed by the bot.

Looking at how many time the bot automatically closed #873, and how many times the issue had to be manually reopened, my opinion if that this bot is counter productive and should be disabled.

Marking issues as stale is ok, closing them is not.