website: update docusaurus

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

website/package.json

@@ -9,8 +9,8 @@
     "deploy": "docusaurus deploy"
   },
   "dependencies": {
-    "@docusaurus/core": "^2.0.0-alpha.56",
-    "@docusaurus/preset-classic": "^2.0.0-alpha.56",
+    "@docusaurus/core": "2.0.0-alpha.71",
+    "@docusaurus/preset-classic": "2.0.0-alpha.71",
     "classnames": "^2.2.6",
     "react": "^16.8.4",
     "react-dom": "^16.8.4"