Fix CAPTCHAs on LimeSurvey

While creating the dummy survey for Icinga (#14859 (closed)) I realized that we’re probably missing PHP libraries if some day we want to use CAPTCHA.

I configured the dummy survey to require a CAPTCHA before opening before I wanted to prevent filling up our database with spam.

I would try installing php-imagick.

Original created by @sajolida on 14860 (Redmine)

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