Moves the PBTS ADR to Accepted list (#9654)

ditto
---

#### PR checklist

- [x] Tests written/updated, or no tests needed
- [x] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [x] Updated relevant documentation (`docs/`) and code comments, or no
      documentation updates needed

docs/architecture/README.md

@@ -78,6 +78,7 @@ Note the context/background should be written in the present tense.
 - [ADR-039: Peer-Behaviour](./adr-039-peer-behaviour.md)
 - [ADR-063: Privval-gRPC](./adr-063-privval-grpc.md)
 - [ADR-067: Mempool Refactor](./adr-067-mempool-refactor.md)
+- [ADR-071: Proposer-Based Timestamps](./adr-071-proposer-based-timestamps.md)
 - [ADR-075: RPC Event Subscription Interface](./adr-075-rpc-subscription.md)
 - [ADR-079: Ed25519 Verification](./adr-079-ed25519-verification.md)
 - [ADR-081: Protocol Buffers Management](./adr-081-protobuf-mgmt.md)
@@ -114,7 +115,6 @@ None
 - [ADR-064: Batch Verification](./adr-064-batch-verification.md)
 - [ADR-068: Reverse-Sync](./adr-068-reverse-sync.md)
 - [ADR-069: Node Initialization](./adr-069-flexible-node-initialization.md)
-- [ADR-071: Proposer-Based Timestamps](./adr-071-proposer-based-timestamps.md)
 - [ADR-073: Adopt LibP2P](./adr-073-libp2p.md)
 - [ADR-074: Migrate Timeout Parameters to Consensus Parameters](./adr-074-timeout-params.md)
 - [ADR-080: Reverse Sync](./adr-080-reverse-sync.md)