Update GraphQL linter

This updates to the next major release of
@graphql-eslint/eslint-plugin@3.0.0. This also updates to
graphql@15.7.2, since a transitive dependency of the linter requires it:

    @graphql-eslint/eslint-plugin
    -> graphql-config
    -> @graphql-tools/url-loader
    -> subscriptions-transport-ws
    -> graphql@^15.7.2 || ^16.0.0"

package.json

@@ -133,7 +133,7 @@
     "fast-mersenne-twister": "1.0.2",
     "file-loader": "^6.2.0",
     "fuzzaldrin-plus": "^0.6.0",
-    "graphql": "^15.4.0",
+    "graphql": "^15.7.2",
     "graphql-tag": "^2.11.0",
     "highlight.js": "^11.3.1",
     "immer": "^7.0.7",
@@ -209,7 +209,7 @@
     "@babel/plugin-transform-modules-commonjs": "^7.10.1",
     "@gitlab/eslint-plugin": "10.0.0",
     "@gitlab/stylelint-config": "2.6.0",
-    "@graphql-eslint/eslint-plugin": "2.3.0",
+    "@graphql-eslint/eslint-plugin": "3.0.0",
     "@testing-library/dom": "^7.16.2",
     "@vue/test-utils": "1.2.0",
     "acorn": "^6.3.0",