build(deps): bump @docusaurus/preset-classic in /website (#626)

Bumps [@docusaurus/preset-classic](https://github.com/facebook/docusaurus/tree/HEAD/packages/docusaurus-preset-classic) from 2.0.0-alpha.70 to 2.0.0-alpha.71.
- [Release notes](https://github.com/facebook/docusaurus/releases)
- [Changelog](https://github.com/facebook/docusaurus/blob/master/CHANGELOG-2.x.md)
- [Commits](https://github.com/facebook/docusaurus/commits/v2.0.0-alpha.71/packages/docusaurus-preset-classic)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

website/package.json

@@ -12,7 +12,7 @@
     },
     "dependencies": {
         "@docusaurus/core": "2.0.0-alpha.70",
-        "@docusaurus/preset-classic": "2.0.0-alpha.70",
+        "@docusaurus/preset-classic": "2.0.0-alpha.71",
         "@mdx-js/react": "^1.6.22",
         "clsx": "^1.1.1",
         "react": "^16.8.4",