strip leftover sdmx key from catalog meta.json

meta.json

@@ -25,6 +25,5 @@
     "builder": "packages/bdp/scripts/build_catalog.py",
     "content_sha256": "44e0108944c9917697b112262032274ecf697c7d15040cf8935a54915669f4ac",
     "manifest_contract_sha256": "5f9b295f01df7c377ccc53bd59e7efdd8361f9140c824bd5018a4c3c2449dd66"
-  },
-  "sdmx": null
-}
+  }
+}