Downgrade GraphQL to fix typescript error

graphql/graphql-js#2490
apollographql/apollo-client#6220

Author: Ni0rd

package.json

@@ -47,7 +47,7 @@
     "eslint-plugin-import": "2.20.2",
     "eslint-plugin-jest": "23.8.2",
     "eslint-plugin-prettier": "3.1.3",
-    "graphql": "15.0.0",
+    "graphql": "14.5.8",
     "graphql-tag": "2.10.3",
     "jest": "25.5.3",
     "micro": "9.3.4",

yarn.lock

@@ -3683,10 +3683,12 @@ graphql-upload@^8.0.2:
     http-errors "^1.7.3"
     object-path "^0.11.4"
 
-[email protected]:
-  version "15.0.0"
-  resolved "https://registry.yarnpkg.com/graphql/-/graphql-15.0.0.tgz#042a5eb5e2506a2e2111ce41eb446a8e570b8be9"
-  integrity sha512-ZyVO1xIF9F+4cxfkdhOJINM+51B06Friuv4M66W7HzUOeFd+vNzUn4vtswYINPi6sysjf1M2Ri/rwZALqgwbaQ==
+[email protected]:
+  version "14.5.8"
+  resolved "https://registry.yarnpkg.com/graphql/-/graphql-14.5.8.tgz#504f3d3114cb9a0a3f359bbbcf38d9e5bf6a6b3c"
+  integrity sha512-MMwmi0zlVLQKLdGiMfWkgQD7dY/TUKt4L+zgJ/aR0Howebod3aNgP5JkgvAULiR2HPVZaP2VEElqtdidHweLkg==
+  dependencies:
+    iterall "^1.2.2"
 
 graphql@^14.5.3:
   version "14.6.0"