Update Podfile to support RN-0.61

[SergioEstevao]

This PR updates the RN libraries references in the podfile Gutenberg section to make sure they follow the new names and needs of the new version.

To test:

• Delete the pods folder: rm -Rf Pods. This updates brings a a lot of pod change for RN so it's better to start with a clean folder.
• Run rake dependencies
• Make sure the project builds
• Make sure you can open a GB post.
• Smoke test the functionality on the GB editor.

PR submission checklist:

• I have considered adding unit tests where possible.

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[etoledom]

• Project builds and run! 🎉
• Gutenberg opens and works well 🎉 🎉

rm -rf Pods was needed to properly run rake dependencies, other than that, everything looks great .
🎉 🎉 🎉

[etoledom]

Let's wait for the WPiOS code freeze to merge this, or target and merge to gutenberg/after-1.21.0.

[hypest]

Yeap, let's target the gutenberg/after-1.21.0 branch (Sérgio already did it in the meantime) so we only merge this to the main app only after the main app freeze.