chore: re-enforce a whitelist policy in the RC relayer (#4032)

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typescript/infra/config/environments/mainnet3/agent.ts

@@ -287,9 +287,7 @@ const releaseCandidate: RootAgentConfig = {
       repo,
       tag: '0d12ff3-20240620-173353',
     },
-    // We're temporarily (ab)using the RC relayer as a way to increase
-    // message throughput.
-    // whitelist: releaseCandidateHelloworldMatchingList,
+    whitelist: releaseCandidateHelloworldMatchingList,
     gasPaymentEnforcement,
     metricAppContexts,
     resources: relayerResources,