The tooltip help regarding the playback rate change buttons stated that
those raise/lower pitch.

If keylock is disabled, this is true, though incomplete, since the
buttons also affect playback speed.
If keylock is enabled, this is false, since pitch is left unchanged, and
only playback speed changes.

This commit replaces the tooltip text about pitch change with text about
playback speed. It also copies the clarification:
"(affects both the tempo and the pitch). If keylock is enabled, only the
tempo is affected."
over from the Speed Control fader tooltip, to prevent further confusion.

Co-authored-by: ronso0 <ronso0@mixxx.org>