strip leftover sdmx key from catalog meta.json

meta.json

@@ -25,6 +25,5 @@
     "builder": "packages/boc/scripts/build_catalog.py",
     "content_sha256": "865f818209b62467c63edef0e79c5de77d51727169d34b48f8e60ffe1e7babcf",
     "manifest_contract_sha256": "687152461d5419a16eb6602f98bf9e2353bdb664f50c22d543ff0373c3021f11"
-  },
-  "sdmx": null
-}
+  }
+}