JCT-147: update SCIM documentation how to deactivate user

[Veki301]

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines

[arthurwolf]

lgtm

[fisx]

Thanks! Could you also add a changelog file under changelog.d/4-docs/pr-2720 that contains just the string "Document user deactivation (aka suspension) with SCIM."?

I would do it myself, but it's your fork. :)

[fisx]

see above comments.

[Veki301]

@fisx added changelog, please merge once checks are done, thank you :)