Fix changelog commit range in v12 migration guide (#1470)

Author: friederbluemle

website/docs/MigrationV12.md

@@ -63,5 +63,5 @@ RNTL v12 introduces `root` API as an alternative that returns a root **host** el
 If you use `toBeOnTheScreen` matcher from [@testing-library/jest-native](https://github.com/testing-library/jest-native) your tests will fail because it uses the `container` api. To fix this, update `@testing-library/jest-native` to version 5.4.2.    
 
 # Full Changelog
-https://github.com/callstack/react-native-testing-library/compare/v11.5.2...v11.5.2...v12.0.0-rc.0
+https://github.com/callstack/react-native-testing-library/compare/v11.5.2...v12.0.0