Remove scrolling left of zero check mark from Tracks menu...

... Less need now to make it more discoverable, because we override an "off"
setting during transport with a pinned play head, thus removing some
inconsistency and confusion.

src/Menus.h

@@ -179,8 +179,6 @@ double GetTime(const Track *t);
 void OnSortTime();
 void OnSortName();
 
-void OnToggleScrollLeftOfZero();
-
 void OnSnapToOff();
 void OnSnapToNearest();
 void OnSnapToPrior();