build: downgrade gatsby to fix test failure

Author: lokesh-coder

docs/package.json

@@ -10,7 +10,7 @@
     "babel-plugin-prismjs": "^2.0.1",
     "babel-preset-gatsby": "^0.4.1",
     "flexboxgrid": "^6.3.1",
-    "gatsby": "^2.21.13",
+    "gatsby": "2.22.12",
     "gatsby-image": "^2.4.1",
     "gatsby-plugin-breadcrumb": "^9.0.2",
     "gatsby-plugin-manifest": "^2.4.2",