Update PR template changelog link (#24919)

Summary:
fix #24917.

## Changelog

[Internal] [Changed] - Update PR template changelog link
Pull Request resolved: https://github.com/facebook/react-native/pull/24919

Differential Revision: D15385773

Pulled By: hramos

fbshipit-source-id: 81a220efc3999942bd41ddf7cbd3107a755cfebd

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,7 +6,7 @@
 
 ## Changelog
 
-<!-- Help reviewers and the release process by writing your own changelog entry. See http://facebook.github.io/react-native/docs/contributing#changelog for an example. -->
+<!-- Help reviewers and the release process by writing your own changelog entry. See https://github.com/facebook/react-native/wiki/Changelog for an example. -->
 
 [CATEGORY] [TYPE] - Message