translation update
fix possible XSS vulnerability in Plugin Manager

The plugin manager echos raw URLs in error messages, this could allow to
construct an XSS attack. However the affected form is CSRF protected,
so an attacker would require another XSS vulnerability to get the needed token,
rendering this attack unneeded. So this should not be exploitable.
Merge pull request #472 from dokuwiki-translate/lang_update_559

Translation update (it)
Revert "Merge pull request #472 from dokuwiki-translate/lang_update_559"

This reverts commit 32eed03cda7768e2efac40f1791c6b967d82778b, reversing
changes made to 9e8bcd5f2ba2246ad2dff46d0313cb0c9e9f5579.

I accidentally hit the wrong button on github :-) This translation added
no new strings and should not have been merged.