Update getLatestRelease.ts to use currentVersion in diffUrl

[kraenhansen]

Summary:

As per 5774e6a#r135571193 I think a copy-paste error happened while refactoring this code. This is the current output printed by the printNewRelease function:

info React Native v0.73.1 is now available (your project is running on v0.73.0).
info Changelog: https://github.com/facebook/react-native/releases/tag/v0.73.1
info Diff: https://react-native-community.github.io/upgrade-helper/?from=0.73.1
info For more info, check out "https://reactnative.dev/docs/upgrading?os=macos".

Note how the from query param of the diff URL uses the stable version instead of the current.

This is the code prior to the commit that introduced the issue:

cli/packages/cli-tools/src/releaseChecker/getLatestRelease.ts

Line 62 in 78a1742

diffUrl: buildDiffUrl(currentVersion),

Test Plan:

This is a simple change, which I applied locally to test it.

Checklist

• Documentation is up to date to reflect these changes.
• Follows commit message convention described in CONTRIBUTING.md

[szymonrybczak]

Thank you! 🙏