Fix overlapping replay slots after a prerender abort #37850

Summary

A prerender can abort during a retry after the retried task has spawned a suspended child. Abort cleanup records a replay slot for the whole task, then tries to record a child slot at the same key path. Resuming the parent already renders that child, so the existing assertion turns a resumable abort into a prerender error. This surfaced after the abort unwind change in #37710.

Keep the parent slot and ignore the redundant child slot. The regression test verifies that both children render after resuming.

How did you test this change?

• 
  yarn test ReactDOMFizzStaticBrowser --runInBand (36 passed)


• 
  yarn test ReactDOMFizzStaticBrowser --prod --runInBand (36 passed)


• yarn linc


• node scripts/prettier/index.js check-changed