When "Show Cursor" is unchecked, the Drivers Editor would still display
the vertical line representing the cursor x.
Probably overseen in rB65072499c65a: Graph Editor: Allow "cursor x" to have fractional values when working with… (historically the vertical line
could represent either the current frame of the cursor X in drawing, but
this is now much more separate).
There is no point in seeing part of the cursor in the Drivers Editor if
this is disabled.
Also correct outdated comments.
ref. T91157