[18] Update React.lazy docs (#4483)

Author: rickhanlonii

content/docs/code-splitting.md

@@ -81,10 +81,6 @@ When using [Babel](https://babeljs.io/), you'll need to make sure that Babel can
 
 ## `React.lazy` {#reactlazy}
 
-> Note:
->
-> `React.lazy` and Suspense are not yet available for server-side rendering. If you want to do code-splitting in a server rendered app, we recommend [Loadable Components](https://github.com/gregberge/loadable-components). It has a nice [guide for bundle splitting with server-side rendering](https://loadable-components.com/docs/server-side-rendering/).
-
 The `React.lazy` function lets you render a dynamic import as a regular component.
 
 **Before:**

content/docs/reference-react.md

@@ -342,10 +342,6 @@ const SomeComponent = React.lazy(() => import('./SomeComponent'));
 
 Note that rendering `lazy` components requires that there's a `<React.Suspense>` component higher in the rendering tree. This is how you specify a loading indicator.
 
-> **Note**
->
-> Using `React.lazy`with dynamic import requires Promises to be available in the JS environment. This requires a polyfill on IE11 and below.
-
 ### `React.Suspense` {#reactsuspense}
 
 `React.Suspense` lets you specify the loading indicator in case some components in the tree below it are not yet ready to render. Today, lazy loading components is the **only** use case supported by `<React.Suspense>`:
@@ -370,10 +366,6 @@ It is documented in our [code splitting guide](/docs/code-splitting.html#reactla
 
 While this is not supported today, in the future we plan to let `Suspense` handle more scenarios such as data fetching. You can read about this in [our roadmap](/blog/2018/11/27/react-16-roadmap.html).
 
->Note:
->
->`React.lazy()` and `<React.Suspense>` are not yet supported by `ReactDOMServer`. This is a known limitation that will be resolved in the future.
-
 ### `React.startTransition` {#starttransition}
 
 ```js