Remove stale deprecation note from unmounting docs

docs/ref-01-top-level-api.md

@@ -53,10 +53,6 @@ boolean unmountComponentAtNode(DOMElement container)
 
 Remove a mounted React component from the DOM and clean up its event handlers and state. If no component was mounted in the container, calling this function does nothing. Returns `true` if a component was unmounted and `false` if there was no component to unmount.
 
-> Note:
->
-> This method was called `React.unmountAndReleaseReactRootNode` until v0.5. It still works in v0.5 but will be removed in future versions.
-
 
 ### React.renderComponentToString