Back out "Show FB internal instructions by default on "Getting Started" page"

Summary: Unfortunately optional require does not work with docusaurus bundler configuration in case file not exist, so open source build is failing now. I'm backing out this commit until solution for dynamic imports in docusaurus found.

Reviewed By: mweststrate

Differential Revision: D23679198

fbshipit-source-id: 9be008f19b5945d17ec31614a8d2cb80bad9ca2e

website/sidebars.js

@@ -29,6 +29,7 @@ module.exports = {
   },
   setup: {
     'Getting Started': [
+      ...fbInternalOnly(['getting-started/fb/using-flipper-at-facebook']),
       'getting-started/index',
       'getting-started/android-native',
       'getting-started/ios-native',

website/src/components/FBContent.jsx

@@ -1,48 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @format
- */
-
-import React from 'react';
-import {isInternal} from 'internaldocs-fb-helpers';
-import Tabs from '@theme/Tabs';
-import TabItem from '@theme/TabItem';
-
-function createElement(createElement) {
-  if (!createElement) return undefined;
-  if (React.isValidElement(createElement)) {
-    return createElement;
-  }
-  const element = createElement();
-  if (React.isValidElement(element)) {
-    return element;
-  }
-  return React.createElement(element.default || element, {});
-}
-
-function FBContent({internal, external}) {
-  if (!isInternal()) {
-    return createElement(external);
-  }
-  if (internal && external) {
-    return (
-      <Tabs
-        defaultValue="internal-docs"
-        values={[
-          {label: 'FB Internal', value: 'internal-docs'},
-          {label: 'Open-Source', value: 'external-docs'},
-        ]}>
-        <TabItem value="internal-docs">{createElement(internal)}</TabItem>
-        <TabItem value="external-docs">{createElement(external)}</TabItem>
-      </Tabs>
-    );
-  } else {
-    return createElement(internal || external);
-  }
-}
-
-export default FBContent;