Upgrade prettier 1.15.1 -> 1.15.2

Author: ehmicky

package-lock.json

@@ -78,7 +78,7 @@
     "npm-path": "^2.0.4",
     "nyc": "^13.1.0",
     "plugin-error": "^1.0.1",
-    "prettier": "^1.15.1",
+    "prettier": "^1.15.2",
     "release-it": "^7.6.3",
     "sinon": "^7.1.1"
   },