Remove explicit context menu width

Firefox and Chromium at least seem to autosize correctly based
on the actual text in use for a given locale.

app/assets/javascripts/index.js

@@ -80,8 +80,7 @@ $(document).ready(function () {
   var map = new L.OSM.Map("map", {
     zoomControl: false,
     layerControl: false,
-    contextmenu: true,
-    contextmenuWidth: 140
+    contextmenu: true
   });
 
   map.attributionControl.setPrefix('');