Update dependency prettier to v1.19.1

Author: renovate-bot

package-lock.json

@@ -63,7 +63,7 @@
     "graphql-tag": "2.10.0",
     "jest": "23.6.0",
     "ncp": "2.0.0",
-    "prettier": "1.15.3"
+    "prettier": "1.19.1"
   },
   "jest": {
     "testEnvironment": "node",