React release script follow-up

[bvaughn]

• Verify that it's safe to run yarn build only once (including extracting errors); see this comment thread for more context. (PR Rollup script can now extract error codes and build in a single pass #11291)
• Decide on a mechanism to relax peer dependency constraints; see React Test Renderer's Peer dependency keeps getting bumped #11278 for more context. (PR Release script no longer auto-updates peerDependencies react version #11292)