[FIX] Removing red on red text when A category is mandatory

Description

Enable mandatory categories Create some categories Try saving a wiki page without choosing a category which leads us to display the background and text of the warring in Red, which is not pleasant to see.

Steps to test

The best solution I could test was to change the class values where the value "A category is mandatory" was taken over, which gives us that :

{tr}A category is mandatory{/tr}

.

Expected result

all the problems related to it have been solved.