fix: check for presence of metadata.allowlist instead of allowlist

reverts a regression introduced in commit
4f6beba where we started checking for
allowlist, instead of metadata.allowlist. We should actually check for
the presence of metadata.allowlist, to prevent the case where the user
specifies both a CID and a json allowlist to the endpoint.

Author: Jipperism

src/controllers/MetadataController.ts

@@ -131,7 +131,7 @@ export class MetadataController extends Controller {
         };
       }
 
-      if (allowList) {
+      if (metadataValidationResult.data.allowList) {
         this.setStatus(409);
         return {
           success: false,