Fix/update ApolloProvider docs (#6625)

* remove unused ApolloProvider mdx import

* inline apollo-provider.mdx into hooks.mdx and update

This removes some instructions and updates the example code to use `@apollo/client`. The code was inlined because it is no longer shared and as a workaround for a possibly unrelated issue.

docs/shared/apollo-provider.mdx

@@ -1,22 +1 @@
-The `ApolloProvider` component leverages [React's Context API](https://reactjs.org/docs/context.html) to make a configured Apollo Client instance available throughout a React component tree. This component can be imported directly from the `@apollo/react-common` package where it lives, or from one of the `@apollo/react-hooks`, `@apollo/react-components`, and `@apollo/react-hoc` packages.
 
-```js
-import { ApolloProvider } from '@apollo/react-hooks';
-```
-
-### Props
-
-| Option   | Type                       | Description                 |
-| -------- | -------------------------- | --------------------------- |
-| `client` | ApolloClient<TCache> | An `ApolloClient` instance. |
-
-### Example
-
-```jsx
-ReactDOM.render(
-  <ApolloProvider client={client}>
-    <MyRootComponent />
-  </ApolloProvider>,
-  document.getElementById('root'),
-);
-```

docs/source/api/react/hoc.mdx

@@ -4,8 +4,6 @@ sidebar_title: 'HOC (deprecated)'
 description: Deprecated React Apollo HOC API
 ---
 
-import ApolloProvider from '../../../shared/apollo-provider.mdx';
-
 > **NOTE:** React Apollo's higher order components have been deprecated. They will continue to receive bug fixes until March 2020, after which they will no longer be maintained by Apollo.
 
 ## Installation

docs/source/api/react/hooks.mdx

@@ -3,7 +3,6 @@ title: Hooks
 description: Apollo Client react hooks API reference
 ---
 
-import ApolloProvider from '../../../shared/apollo-provider.mdx';
 import QueryOptions from '../../../shared/query-options.mdx';
 import QueryResult from '../../../shared/query-result.mdx';
 import MutationOptions from '../../../shared/mutation-options.mdx';
@@ -17,7 +16,28 @@ Apollo Client >= 3 includes React hooks functionality out of the box. You don't
 
 ## `ApolloProvider`
 
-<ApolloProvider />
+The `ApolloProvider` component leverages [React's Context API](https://reactjs.org/docs/context.html) to make a configured Apollo Client instance available throughout a React component tree. This component can be imported directly from the `@apollo/client` package.
+
+```js
+import { ApolloProvider } from '@apollo/client';
+```
+
+### Props
+
+| Option   | Type                       | Description                 |
+| -------- | -------------------------- | --------------------------- |
+| `client` | ApolloClient&lt;TCache&gt; | An `ApolloClient` instance. |
+
+### Example
+
+```jsx
+ReactDOM.render(
+  <ApolloProvider client={client}>
+    <MyRootComponent />
+  </ApolloProvider>,
+  document.getElementById('root'),
+);
+```
 
 ## `ApolloConsumer`