🔪 obsolete spikes <--> hovermode logic

- This is an artefact from the early days of "spikes" where
  they only worked with hovermode:'closest'

Author: etpinard

src/components/modebar/buttons.js

@@ -253,13 +253,6 @@ function handleCartesian(gd, ev) {
         if(astr === 'hovermode' && (val === 'x' || val === 'y')) {
             val = fullLayout._isHoriz ? 'y' : 'x';
             button.setAttribute('data-val', val);
-        } else if(astr === 'hovermode' && val === 'closest') {
-            for(i = 0; i < axList.length; i++) {
-                ax = axList[i];
-                if(allSpikesEnabled === 'on' && !ax.showspikes) {
-                    allSpikesEnabled = 'off';
-                }
-            }
         }
 
         aobj[astr] = val;