chore(deps-dev): bump eslint-plugin-graphql in /tests/demo (#790)

Bumps [eslint-plugin-graphql](https://github.com/apollostack/eslint-plugin-graphql) from 2.1.1 to 3.1.0.
- [Release notes](https://github.com/apollostack/eslint-plugin-graphql/releases)
- [Changelog](https://github.com/apollographql/eslint-plugin-graphql/blob/master/CHANGELOG.md)
- [Commits](https://github.com/apollostack/eslint-plugin-graphql/commits)

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

tests/demo/package.json

@@ -28,7 +28,7 @@
     "@vue/cli-plugin-eslint": "^3.1.4",
     "@vue/cli-service": "^3.1.3",
     "@vue/eslint-config-standard": "^4.0.0",
-    "eslint-plugin-graphql": "^2.1.1",
+    "eslint-plugin-graphql": "^3.1.0",
     "graphql-tag": "^2.5.0",
     "start-server-and-test": "^1.10.2",
     "stylus": "^0.54.5",

tests/demo/yarn.lock

@@ -4362,10 +4362,10 @@ eslint-plugin-es@^1.3.1:
     eslint-utils "^1.4.2"
     regexpp "^2.0.1"
 
-eslint-plugin-graphql@^2.1.1:
-  version "2.1.1"
-  resolved "https://registry.yarnpkg.com/eslint-plugin-graphql/-/eslint-plugin-graphql-2.1.1.tgz#dae5d597080075320ea8e98795056309ffe73a18"
-  integrity sha512-JT2paUyu3e9ZDnroSshwUMc6pKcnkfXTsZInX1+/rPotvqOLVLtdrx/cmfb7PTJwjiEAshwcpm3/XPdTpsKJPw==
+eslint-plugin-graphql@^3.1.0:
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/eslint-plugin-graphql/-/eslint-plugin-graphql-3.1.0.tgz#ccf0d3c61961f6307170ac565c1fb0902dd4f11f"
+  integrity sha512-87HGS00aeBqGFiQZQGzSPzk1D59w+124F8CRIDATh3LJqce5RCTuUI4tcIqPeyY95YPBCIKwISksWUuA0nrgNw==
   dependencies:
     graphql-config "^2.0.1"
     lodash "^4.11.1"