Note about hidden folders when exceeding disk quota

[rkronberg]

Proposed changes

There are quite often tickets where users struggle with disk quota exceeded errors and do not understand why moving/deleting files does not have any effect on the situation. Frequently the issue is a large number of files in hidden folders.

https://csc-guide-preview.rahtiapp.fi/origin/quota-exceeded/support/faq/disk-quota-exceeded/

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