[Flaky CI]: Cloudflare Integration Tests - suites/tracing/instrument-fetcher/test.ts > stub.fetch: headers on Request (URL from incoming request)

### Flakiness Type

Other / Unknown

### Name of Job

Cloudflare Integration Tests

### Name of Test

suites/tracing/instrument-fetcher/test.ts > stub.fetch: headers on Request (URL from incoming request)

### Link to Test Run

https://github.com/getsentry/sentry-javascript/actions/runs/34100281691/job/101673496119

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_This issue was automatically created._

Start with suites/tracing/instrument-fetcher/test.ts and the failing stub.fetch case, then inspect the linked Cloudflare Integration Tests run. Reproduce the failure locally or in CI and identify why headers on Request differ for an incoming-request URL. Done means the test is reliable and the Cloudflare integration job passes consistently.

Written by the indexing model from the issue text.