don't use `<h*>` tags for styling text

#336 (closed) found some places where <h4> and <h5> tags were being used to style text. this is contrary to the way those tags should be used, and can cause issues for e.g. users with screenreaders and violates WCAG 2.4 guidelines (criteria 2.4.6)

i've closed that ticket, but the issue still exists elsewhere. heading tags are being used for styling (padding, font-size, etc.) and that's breaking the semantics of the page. bootstrap makes this easy to fix by providing the .h1 through .h6 classes, which can be used to style an element like a heading, without breaking the page semantics.

we should comb through templates looking for headings that break the page semantics, and fix those