help-overlay.ui: use action-name, instead of accelerator

To unifiy the source, use action-name, instead of accelerator
3 jobs for helpoverlay in 4 minutes and 34 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #607279
build-and-test

00:03:00

passed #626553
flatpak
flatpak

00:01:33

failed #607280
flatpak
flatpak

00:00:18