fix(sdmx_series_ecb_bnt): refresh content digest after key strip

sdmx_series_ecb_bnt/meta.json

@@ -42,8 +42,8 @@
   "build": {
     "built_at": "2026-06-18T22:29:00.416343Z",
     "parsimony_version": null,
-    "builder": null,
-    "content_sha256": "55086258505bd6b43217d4b50cfbf0ac501c82f3f651207758c21c4baef39951",
+    "builder": "strip-ecb-flow-prefix-keys",
+    "content_sha256": "04205a1bc2b1a68b27c3b060d8760c1ae50368a0f62e7dd254ada33c3a769881",
     "manifest_contract_sha256": "7fd1c9935c61287fe4e14a08d0232c477cb5760be276910dfa8abb1232984c3f"
   }
 }