fix tick0 bug introduced in previous commit a4cb02b

Author: archmoj

src/plots/cartesian/axes.js

@@ -709,16 +709,11 @@ axes.calcTicks = function calcTicks(ax, opts) {
         }
 
         if(prevDtick !== ax.dtick && ax._tick0Init !== ax.tick0) {
-            var prevTick0 = ax.tick0;
-
             // move tick0 back
             ax.tick0 = axes.tickIncrement(ax.tick0, prevDtick, !axrev, ax.calendar);
 
             // redo first tick
             ax._tmin = axes.tickFirst(ax, opts);
-
-            // maintain tick0 value
-            ax.tick0 = prevTick0;
         }
     }