errors: errors.Join behavior changed in 1.25 [1.25 backport]

[gopherbot]

@neild requested issue #76961 to be considered for backport to the next 1.25 minor release.

@gopherbot please open backport issues for go1.25 and go1.26.

(We should fix this in 1.26. I'm not certain if backporting to 1.25 is the right choice or not, but let's open the issue to decide.)