fix(sdmx_series_ecb_wts): refresh content digest after key strip

sdmx_series_ecb_wts/meta.json

@@ -45,8 +45,8 @@
   "build": {
     "built_at": "2026-06-18T22:35:33.730749Z",
     "parsimony_version": null,
-    "builder": null,
-    "content_sha256": "783a4dec1fd89dd3c8f9513d2902e155ed9cbfbad489574858148c3a2e6a6efb",
+    "builder": "strip-ecb-flow-prefix-keys",
+    "content_sha256": "3ac2b46e737212e76df902497648ec90529aa488a9f5abfd8dc9041b6889cb5b",
     "manifest_contract_sha256": "99d070c927edd66cfc05ed9eb9420764da28b58c152c35a57158dfe80f9711dd"
   }
 }