fix: remove $apisix_request_id from stream access_log_format

[Copilot]

Follow-up to #255 — $apisix_request_id is not available in the stream (L4) context. Remove it from the default stream access_log_format.

• values.yaml: Stream accessLogFormat changed to $remote_addr [$time_local] $protocol $status $bytes_sent $bytes_received $session_time
• Chart.yaml: Version bump 0.2.52 → 0.2.53
• README.md: Regenerated via make helm-docs

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