Flaky test: tests/sentry/sentry_metrics/test_all_indexers.py::test_rate_limited[UseCaseID.TRANSACTIONS-PGStringIndexerV2]

Failing test: `tests/sentry/sentry_metrics/test_all_indexers.py::test_rate_limited[UseCaseID.TRANSACTIONS-PGStringIndexerV2]`
Sentry sha: abdb2eeccb973e9b33600d0fb95e18b12b995415
Run: https://github.com/getsentry/sentry/actions/runs/22208450954

```
tests/sentry/sentry_metrics/test_all_indexers.py:532: in test_rate_limited
assert results[use_case_id][1] == {"x": None, "y": None, "z": None}
E AssertionError: assert {'x': None, '...35, 'z': None} == {'x': None, '...ne, 'z': None}
E 
E Omitting 2 identical items, use -vv to show
E Differing items:
E {'y': 35} != {'y': None}
E 
E Full diff:
E {
E 'x': None,
E - 'y': None,
E ? ^^^^
E + 'y': 35,
E ? ^^
E 'z': None,
E }
```

Start by running tests/sentry/sentry_metrics/test_all_indexers.py::test_rate_limited[UseCaseID.TRANSACTIONS-PGStringIndexerV2] and inspect the failure around line 532. Investigate why the result contains y=35 instead of None for this indexer, then confirm the test passes consistently and preserves the expected rate-limited result.

Written by the indexing model from the issue text.