chore(ci): flag ProvingBroker "does not retry if job is stale" as flake (#23047)

Flagging `ProvingBroker > Retries > does not retry if job is stale` as a
flake in `.test_patterns.yml`. Failure surfaced on an unrelated wallet
PR — `dbanks12`'s wallet refactor — at
http://ci.aztec-labs.com/64a972aafaa40dd0.

## Failure

```
● ProvingBroker › Retries › does not retry if job is stale

  Store is closed

  > 99 |             throw new Error('Store is closed');
        |                   ^

  at AztecLMDBStoreV2.transactionAsync (yarn-project/kv-store/dest/lmdb-v2/store.js:99:19)
  at SingleEpochDatabase.transactionAsync [as batchWrite]
    (yarn-project/prover-client/src/proving_broker/proving_broker_database/persisted.ts:45:22)
  at KVBrokerDatabase.batchWrite [as commitWrites]
    (yarn-project/prover-client/src/proving_broker/proving_broker_database/persisted.ts:120:14)
```

The broker tries to commit the final `reportProvingJobError` write after
the per-epoch LMDB store has already been closed (the test advances the
epoch from 1 → 3, which causes the epoch-1 store to be torn down). The
race is between the epoch advance / cleanup path and the final error
write — a timing flake, not a logic bug.

## Owner

Test was authored by `@alexghr` in #9400 (`feat: new proving broker
implementation`) and most recently edited by `@alexghr` in #22508
(`fix(prover-client): don't mark in-progress epoch N jobs as stale when
epoch N+1 starts`). `@spypsy` has also recently fixed retries-related
races in this file (#21842, #22355). Pinging Alex as primary owner; tag
Spyros if it's actually a retry-counter race rather than a
store-lifecycle race.

## Other branches

Spot-checked the most recent failed runs on `merge-train/fairies` and
`merge-train/spartan` — none of them hit this same `proving_broker` /
`Store is closed` failure in the data window I sampled. The flake has
only been observed on the one wallet PR run linked above so far.

## Pattern entry

The new entry uses both `regex` (test file path) and `error_regex`
(`does not retry if job is stale|Store is closed`) so unrelated failures
in `proving_broker.test.ts` still fail CI — only this specific timing
race gets quarantined to a Slack ping.

---
*Created by
[claudebox](https://claudebox.work/v2/sessions/b4b6eb63ff789d29) ·
group: `aztec`*

Author: dbanks12

.test_patterns.yml

@@ -188,6 +188,14 @@ tests:
       - *phil
       - *palla
 
+  # http://ci.aztec-labs.com/64a972aafaa40dd0
+  # ProvingBroker › Retries › does not retry if job is stale — kv-store closes
+  # before the broker's final reportProvingJobError write lands.
+  - regex: "prover-client/src/proving_broker/proving_broker.test.ts"
+    error_regex: "does not retry if job is stale|Store is closed"
+    owners:
+      - *alex
+
   # Nightly GKE tests
   - regex: "spartan/bootstrap.sh"
     owners: