Fix path not properly being shown without RnDiffApp

[lucasbento]

Summary

There was some sort of change when generating releases that caused the diff to change as following:

Which led upgrade-helper to show the header as:

It seems like the lib we use for parsing diff doesn't like the lack of those initial characters so I had to add some replaces here and there as well as maintain the RnDiffApp replace for the previous versions.

Test Plan

• Open the dev preview;
• Make sure that the paths are rendering correctly without the leading RnDiffApp but still using in specific places (such as RnDiffApp.xcodeproj);
• Set a different app name;
• Make sure that it renders correctly with the different app name.

What are the steps to reproduce?

Checklist

• I tested this thoroughly
• I added the documentation in README.md (if needed)