activate alert boxes in static_severity vignette

[avallecam]

In estimate_static_severity vignette, sth is happening with the alert boxes for:

• use case
• what we have
• concept...

This is how it looks to me:

I think the expected look is like in estimate_time_varying_severity vignette:

[pratikunterwegs]

Thanks for pointing this out - I also noticed this but thought that it might be an issue wit rendering locally on my system. I'm not sure what causes the highlighting to not show, but I will try and figure it out.