Use possessive 'its' not 'it's'

Summary:
Very simple documentation grammar update.
Closes https://github.com/facebook/react-native/pull/14567

Differential Revision: D5269433

Pulled By: hramos

fbshipit-source-id: 2cf38166f53d01fa2465da2b25a3247312dabfb7

Libraries/Lists/FlatList.js

@@ -287,7 +287,7 @@ type DefaultProps = typeof defaultProps;
  *     }
  *
  * This is a convenience wrapper around [`<VirtualizedList>`](docs/virtualizedlist.html),
- * and thus inherits it's props (as well as those of `ScrollView`) that aren't explicitly listed
+ * and thus inherits its props (as well as those of `ScrollView`) that aren't explicitly listed
  * here, along with the following caveats:
  *
  * - Internal state is not preserved when content scrolls out of the render window. Make sure all