Availability settings URL has changed in NC 26

[tcitworld]

Steps to reproduce

1. Try to access personal availability settings from the bottom left settings

Expected behavior

Access the settings

Actual behaviour

Blank page.

In NC26+, /settings/user/groupware is now at /settings/user/availability

[tcitworld]

Needs logic to rewrite the URL depending on the version at

calendar/src/components/AppNavigation/Settings.vue

Line 267 in 999601e

return generateUrl('/settings/user/groupware')