Fix: Set important to override bootstrap h4

[machikoyasuda]

closes #2601

Bootstrap has a class called h4, which has different sizing than what we want.

I could have done a few things:

• Rename the h4 class in our styles
• Use this disable-rfs class that Bootstrap gives you
• Or add important to the existing h4 size declaration

I decided to go with the latter, so that any future use of h4 will be covered (and not require the dev to know to use disable-rfs). I didn't want to rename all the hX classes.

[github-actions]

Coverage report

This PR does not seem to contain any modification to coverable code.

[angela-tran]

Did you find out anything about why it only happens on Chrome?

Oh, I remember now from the notes on #2603 that it has to do with responsive font sizing

[angela-tran]

I'm not able to reproduce the issue on Linux, so I can't test this myself. From that and the ticket description, I'm guessing that this is an macOS / Chrome - specific issue.

The reasoning for using !important sounds good to me.