Summary:
While we're waiting for 19 stable, let's bring main back to 18.3.1 ahead of the 0.77 branch cut. We'll land this change just after 19 stable lands.
This is a cherry pick of b93b378fa0 which landed in 0.76 already
bypass-github-export-checks
## Changelog:
[INTERNAL] - Revert React 19RC to React 18.3.1
Pull Request resolved: https://github.com/facebook/react-native/pull/47380
Test Plan: CI
Reviewed By: cipolleschi
Differential Revision: D65430775
Pulled By: cortinico
fbshipit-source-id: f0f211754c8ffe5d037fd299e4de52c29d1d7913