old link to outdated version of jest (#2088)

This link is pointing to a much older version of Jest. I have added a link to the current page for snapshot testing for the current version of jest.

content/docs/reference-test-renderer.md

@@ -38,7 +38,7 @@ console.log(testRenderer.toJSON());
 //   children: [ 'Facebook' ] }
 ```
 
-You can use Jest's snapshot testing feature to automatically save a copy of the JSON tree to a file and check in your tests that it hasn't changed: [Learn more about it](https://facebook.github.io/jest/blog/2016/07/27/jest-14.html).
+You can use Jest's snapshot testing feature to automatically save a copy of the JSON tree to a file and check in your tests that it hasn't changed: [Learn more about it](https://jestjs.io/docs/en/snapshot-testing).
 
 You can also traverse the output to find specific nodes and make assertions about them.