Update dependency graphql to v15.1.0

Author: renovate-bot

package-lock.json

@@ -25,7 +25,7 @@
     "@babel/register": "7.10.1",
     "babel-eslint": "10.1.0",
     "eslint": "6.8.0",
-    "graphql": "15.0.0",
+    "graphql": "15.1.0",
     "mocha": "7.2.0",
     "pretty-quick": "2.0.1",
     "test-all-versions": "4.1.1"