fix(sdmx_series_ecb_mms): refresh content digest after key strip

sdmx_series_ecb_mms/meta.json

@@ -48,8 +48,8 @@
   "build": {
     "built_at": "2026-06-18T22:32:12.372723Z",
     "parsimony_version": null,
-    "builder": null,
-    "content_sha256": "6e66e6c4a2f63420566c4f06479171d3892be62e0a37f4bddc0175750996608a",
+    "builder": "strip-ecb-flow-prefix-keys",
+    "content_sha256": "e361824ac03b90f1bad28e60a75c17bbde95ffcb36e0db2941771970de8e8c0b",
     "manifest_contract_sha256": "5fd4ba1ca8638f9b3c46e6b9da2c623b0721ca5c952345e4168555ccd1f6a61e"
   }
 }