Update docusaurus dependencies (#419)

Summary:
All bumps are within range, so this shouldn't introduce any breaking
changes.
Pull Request resolved: https://github.com/facebook/flipper/pull/419

Reviewed By: danielbuechele

Differential Revision: D15120854

Pulled By: passy

fbshipit-source-id: dee4b52947cb548d13cd4bf625b29e3a643d8fc3

website/package.json

@@ -14,7 +14,7 @@
     "docblock-parser": "^1.0.0",
     "docusaurus": "^1.0.9",
     "glob": "^7.1.3",
-    "react-docgen": "^3.0.0-rc.1"
+    "react-docgen": "^4.1.0"
   },
   "dependencies": {}
 }

website/static/css/custom.css

@@ -9,15 +9,6 @@ h5,
 h6 {
   font-family: 'San Francisco', -apple-system, BlinkMacSystemFont,
     '.SFNSText-Regular', 'Helvetica Neue', Helvetica, sans-serif;
-  font-size: 17px;
-  font-weight: 400;
-}
-
-.fixedHeaderContainer header h2 {
-  font-family: 'San Francisco', -apple-system, BlinkMacSystemFont,
-    '.SFNSText-Regular', 'Helvetica Neue', Helvetica, sans-serif;
-  font-size: 17px;
-  font-weight: 400;
 }
 
 .splash {