Hello Dolly: Hide the lyrics in the block editor.

I'm sorry, Hello Dolly. You're my favorite plugin, but the way you output your lyrics doesn't play nicely with the block editor, particuarly on mobile devices.

This isn't Farewell Dolly, you're still on every other admin page, and I know you'll come back better and stronger.

Merges [43900] to trunk.

Props joen.
See #45345.
Built from https://develop.svn.wordpress.org/trunk@44229


git-svn-id: https://core.svn.wordpress.org/trunk@44059 1a063a9b-81f0-0310-95a4-ce76da25c4cd