fix(dot.js): fix dotted note dot y-shifting infinitely on repeated rendering
fix(dot.js): fix dotted note dot y-shifting infinitely on repeated rendering

fixes bug introduced by d8763b9
rest note and stave note shiftY seems to be handled differently, stave notes remember previous y-shift.
the dot_shiftY could also be refactored to operate the same for stave notes and rests (= vs +=)

Tails/vexflow,Tails/vexflow,Tails/vexflow