Releasing knewstuff 5.91.1

[Aleix Pol]

Hi David Faure,
As you might have seen, there has been some changes to mitigate a
problem with how some applications are accessing our servers.

https://invent.kde.org/frameworks/knewstuff/-/commit/c8165b7a0d622e318b3353ccf257a8f229dd12c9
https://invent.kde.org/frameworks/knewstuff/-/commit/e1c6f2bf383876a31cd3e3f9e6edcaa19dc0a7dd

We sent an e-mail to distributions asking if they could backport the
offending patches and some asked if we could do a patch release of
knewstuff which I'd say makes sense.

David, would you be able to look into it?

Thanks in advance!
Aleix