Fixed type in docs/Screen Lifecycle page (#6202)

There was a spelling error in 'lifecycle' which is now fixed.

website/docs/docs-screen-lifecycle.mdx

 * `componentDidAppear` - called each time a component is revealed to the user
 * `componentDidDisappear` - called each time a component is hidden from user's view **as a result of being detached from hierarchy**
 
-These methods compliment React's liefcycle methods:
+These methods compliment React's lifecycle methods:
 
 * `componentDidMount` - called once, when a component is attached to hierarchy **for the first time**
 * `componentWillUnmount` - called once, when a component is destroyed