fix(sdmx_series_ecb_efs): refresh content digest after key strip

sdmx_series_ecb_efs/meta.json

@@ -30,8 +30,8 @@
   "build": {
     "built_at": "2026-06-18T22:30:15.508104Z",
     "parsimony_version": null,
-    "builder": null,
-    "content_sha256": "c8d4aea5e25cb462af1e7ad54983cbcf899767ba52e907e47d1e46e049ac1ade",
+    "builder": "strip-ecb-flow-prefix-keys",
+    "content_sha256": "8dc478af5861c80e238f4b5d0b1296c69e7804eb12d9264cfe1a7e1c1c7eb99d",
     "manifest_contract_sha256": "7f3288f00a86f85b95ed063388d4013a8a69e709401a96e7da6aa54ca88928e4"
   }
 }