use valType of angle for pie rotation

Author: archmoj

src/traces/pie/attributes.js

@@ -276,9 +276,7 @@ module.exports = {
         ].join(' ')
     },
     rotation: {
-        valType: 'number',
-        min: -360,
-        max: 360,
+        valType: 'angle',
         dflt: 0,
         editType: 'calc',
         description: [

test/plot-schema.json

@@ -41129,9 +41129,7 @@
      "description": "Instead of the first slice starting at 12 o'clock, rotate to some other angle.",
      "dflt": 0,
      "editType": "calc",
-     "max": 360,
-     "min": -360,
-     "valType": "number"
+     "valType": "angle"
     },
     "scalegroup": {
      "description": "If there are multiple pie charts that should be sized according to their totals, link them by providing a non-empty group id here shared by every trace in the same group.",