Let's remove the DEV flag from Group block and open it to prod.

To Test:

• Generate bundles
• Open WPiOS and WPAndroid PRs
• Verify Group block is visible in the block picker
• Verify it is working as expected, try to break it, use try portrait & landscape modes and try nesting it more than expected

note: We don't need to merge WPiOS and WPAndroid PRs, we can use them for testing purposes.