test(cloudflare): ignore transaction envelope in double-instrumentation flake (#21095)

## Summary

Fixes the flaky `suites/double-instrumentation/test.ts > Only sends one
error event when withSentry is called twice` test in the Cloudflare
Integration Tests job.

## Root cause

When the worker throws on `/error`, two envelopes are produced inside
the same request:

1. The `http.server` span ends (`startSpanManual` in
`packages/cloudflare/src/request.ts`) → a **transaction** envelope is
queued.
2. `captureException(...)` is called → an **event** envelope is queued.

The Cloudflare transport buffers task producers in an
`IsolatedPromiseBuffer` and drains them concurrently via `Promise.all`
during `flushAndDispose`. Both envelopes are POSTed in parallel to the
mock Sentry server, so the order in which they reach the test runner's
`newEnvelope` callback is non-deterministic.

The test only declares one expectation (the error event) and does not
ignore transactions. When the transaction envelope happens to arrive
first, the runner pops the expected event-envelope matcher and asserts
it against the transaction payload — which mismatches on `type: 'event'`
vs `type: 'transaction'` and rejects the run.

Other tests that exercise the same path (e.g.
`suites/hono-integration/test.ts`) handle this by expecting both
envelopes with `.unordered()`. Here the test only asserts on the error
event, so the smallest fix is to add `.ignore('transaction')` — matching
the runner's existing default ignore list (`session`, `sessions`,
`client_report`). The error-event shape assertions are unchanged.

Fixes #21046

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Jan Peer Stöcklmair <jan.peer@sentry.io>

Author: github-actions[bot]

dev-packages/cloudflare-integration-tests/suites/double-instrumentation/test.ts

@@ -26,6 +26,10 @@ it('Only sends one error event when withSentry is called twice', async ({ signal
         },
       }),
     )
+    // The http.server span produces a transaction envelope that is sent in parallel with the
+    // error event. Either can arrive first at the mock server, so ignore it here to keep the
+    // assertion focused on the error event.
+    .ignore('transaction')
     .start(signal);
   await runner.makeRequest('get', '/error', { expectError: true });
   await runner.completed();