Bump docs theme

Author: Stephen Barlow

docs/package.json

@@ -8,7 +8,7 @@
   },
   "dependencies": {
     "gatsby": "2.32.13",
-    "gatsby-theme-apollo-docs": "5.3.3",
+    "gatsby-theme-apollo-docs": "5.3.6",
     "react": "17.0.2",
     "react-dom": "17.0.1",
     "webpack-virtual-modules": "0.4.3"