fix(sdmx_series_ecb_ssp): refresh content digest after key strip

sdmx_series_ecb_ssp/meta.json

@@ -45,8 +45,8 @@
   "build": {
     "built_at": "2026-06-18T22:35:17.325681Z",
     "parsimony_version": null,
-    "builder": null,
-    "content_sha256": "0ef68fcc4aa710f14f72103e1a17741427f63303f6b81493e623f40d31d59a8d",
+    "builder": "strip-ecb-flow-prefix-keys",
+    "content_sha256": "cd50ddb8580cc89c7250b4cf003212a87ee7555f11e94c28fe9d2cb7c11c538f",
     "manifest_contract_sha256": "554bbbbf4f085826bf081fe2f713d6da03171f80b00ce3a876b474ed58742acb"
   }
 }