fix(sdmx_series_ecb_bsp): refresh content digest after key strip

sdmx_series_ecb_bsp/meta.json

@@ -54,8 +54,8 @@
   "build": {
     "built_at": "2026-06-18T22:29:18.839568Z",
     "parsimony_version": null,
-    "builder": null,
-    "content_sha256": "1d5133048354cfd5e5e74582bb5742e5b50a67bb2060c4f28e988c90512f8ca1",
+    "builder": "strip-ecb-flow-prefix-keys",
+    "content_sha256": "75a379291c7cd6eeee928616fe3774f5d460cbf7b6ea06f902b77b812409df02",
     "manifest_contract_sha256": "991613a634bcc9ec61bb686ec082f60f40e25117c7fd321a619a9abb4fdfc73b"
   }
 }