Revert custom_fields_by_lua on audit-log: broke logging entirely

kong.request.get_raw_body()/kong.response.get_raw_body() cannot be
called from the log phase (confirmed via dataplane error logs:
"function cannot be called in log phase") — this silently killed
log_by_lua for every plugin on the request, not just body capture.
Back to metadata-only logging while body capture gets redone properly
(pre-function/post-function storing into kong.ctx.shared, read back
in custom_fields_by_lua).

kong/mcp/audit-log.yaml

@@ -4,12 +4,9 @@ metadata:
   name: ${NAME}-catalog-mcp-audit-log
   namespace: ${NAMESPACE}
 plugin: http-log
-# dev only: request/response bodies and the raw Authorization (JWT) header
-# are captured in clear text. Not acceptable as-is for a non-dev environment.
+# dev only: the raw Authorization (JWT) header is captured in clear text,
+# not acceptable as-is for a non-dev environment.
 config:
   http_endpoint: ${AUDIT_LOG_ENDPOINT}
   method: POST
   content_type: application/json
-  custom_fields_by_lua:
-    request_body: "return kong.request.get_raw_body()"
-    response_body: "return kong.response.get_raw_body()"