Disable parallel transitions in canary

[everettbu]

Mirror of facebook/react#35709
Original author: rickhanlonii

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Accidentally enabled this

[greptile-apps]

Greptile Overview

Greptile Summary

• Disables enableParallelTransitions by default in the canary/shared feature flags.
• Aligns canary behavior with the intended default after the flag was accidentally turned on.
• Change is isolated to packages/shared/ReactFeatureFlags.js; forked flag files remain unchanged.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk.
• Single-line feature flag flip in the central canary flag file; no API surface changes, and existing tests/gating patterns already account for both enabled/disabled states.
• No files require special attention

Important Files Changed

Filename	Overview
packages/shared/ReactFeatureFlags.js	Flips enableParallelTransitions default from true to false in the canary feature flags file.

[greptile-apps]

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[everettbu]

Upstream PR was closed or merged. Code is synced via branch mirror.