Revert "Add some notes about navigation with keys"

This reverts commit 9b3b597.

Author: sonaye

docs/navigating.md

@@ -84,6 +84,7 @@ Let's suppose that we actually *want* to add another details screen. This is pre
   title="Go to Details... again"
   onPress={() => this.props.navigation.push('Details')}
 />
+}
 ```
 
 <a href="https://snack.expo.io/@react-navigation/pushing-details-v2" target="blank" class="run-code-button">&rarr; Run this code</a>
@@ -126,17 +127,6 @@ class DetailsScreen extends React.Component {
 
 Another common requirement is to be able to go back _multiple_ screens -- for example, if you are several screens deep in a stack and want to dismiss all of them to go back to the first screen. In this case, we know that we want to go back to `Home` so we can use `navigate('Home')` (not `push`! try that out and see the difference). Another alternative would be `navigation.popToTop()`, which goes back to the first screen in the stack.
 
-Navigation actions behave idempotently when called with a key. When pushing, the navigator will push a route with that key. If the route already exists, it will navigate to that route and set the params.
-
-```js
-<Button
-  title="Go to Details... but don't push it to the stack if it already exists, just navigate"
-  onPress={() => this.props.navigation.navigate({ routeName: 'Details', key: 'myKey' })}
-/>
-```
-
-In a StackNavigator, you can set the key for initial route by passing `initialRouteKey` to the stack configs object if needed.
-
 ## Summary
 
 * `this.props.navigation.navigate('RouteName')` pushes a new route to the stack navigator if it's not already in the stack, otherwise it jumps to that screen.