Bump graphql from 14.7.0 to 15.4.0

Bumps [graphql](https://github.com/graphql/graphql-js) from 14.7.0 to 15.4.0.
- [Release notes](https://github.com/graphql/graphql-js/releases)
- [Commits](graphql/graphql-js@v14.7.0...v15.4.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -31,7 +31,7 @@
     "@octokit/webhooks": "^7.15.1",
     "@slack/webhook": "^5.0.3",
     "flow-bin": "^0.138.0",
-    "graphql": "^14.0.0"
+    "graphql": "^15.4.0"
   },
   "devDependencies": {
     "@types/jest": "^26.0.0",