Remove `role="presentation"` from headings in the customizer. These were needed to avoid confusing semantics when the headings also acted as buttons to control accordions, changed in [59924].
Change responsive CSS to use `screen-reader-text` styling rather than `display: none` so that mobile retains the headings hierarchy.
Props joedolson, hbhalodia, mikinc860, guillaumeturpin, rcreators, tirth03, dhrumilk .
Fixes#62215.
Built from https://develop.svn.wordpress.org/trunk@59825
git-svn-id: http://core.svn.wordpress.org/trunk@59167 1a063a9b-81f0-0310-95a4-ce76da25c4cd