chore: pin wait-on to 3.2.0 (#1251)

Author: watson

package.json

@@ -165,7 +165,7 @@
     "typescript": "^3.5.2",
     "untildify": "^4.0.0",
     "util.promisify": "^1.0.0",
-    "wait-on": "^3.1.0",
+    "wait-on": "3.2.0",
     "ws": "^7.0.1"
   },
   "greenkeeper": {