fix(sdmx_series_ecb_agr): refresh content digest after key strip

sdmx_series_ecb_agr/meta.json

@@ -45,8 +45,8 @@
   "build": {
     "built_at": "2026-06-18T22:28:48.193618Z",
     "parsimony_version": null,
-    "builder": null,
-    "content_sha256": "a899c9f9a6e1dba7d2a4b428a8515789889f7b01d1c7227279d2249a3dabe8d4",
+    "builder": "strip-ecb-flow-prefix-keys",
+    "content_sha256": "4250b1fc8bc6f15f5d0127934ea1768fe8dd2b641fc0b1bbe547ebaecc8b3d7e",
     "manifest_contract_sha256": "fba6dbccb2e69b4c295d11599ac9db05e76d3e817c6493b48bba97be8c869586"
   }
 }