Change note to warning in documentation

[ghost]

Follow-up of: owncloud-archive/documentation#1981

Warnings currently looks like seen here: https://doc.owncloud.org/server/9.0/admin_manual/issues/code_signing.html#errors

[mention-bot]

By analyzing the blame information on this pull request, we identified @danimo, @dragotin and @carlaschroder to be potential reviewers

[ghost]

@RealRancor

Thanks a lot for your contribution!
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[dragotin]

@carlaschroder your call, please.

[guruz]

@icewind1991 Can you help us with this one?

I wonder if the (original part) is actually true... or shall we mention that the original part is especially valid if filesystem_check_changes is 0?

[ghost]

@guruz The original part is there since ages and long before filesystem_check_changes was set to 0 as the default. So a clarification definitely makes sense.

[guruz]

                                                                                  Would you like to add the occ scan command or a link to it? Like "if you modified, you need to run..." or so?                                                                                                                                                                                                                                                                                                                                        

[ghost]

Thanks for merging. I think this is getting even more important as discussed here: owncloud/core#23783

[guruz]

oh well.. :-|