How do I configure a custom Update Center to not require a certificate?

In my installation of Jenkins 2.346.2, I have configured a local Update Center as the host itself is completely isolated from the Internet. To do this, I have created and hosted my own update-center.json file (with just one plugin for now):
  "id": "default",
  "plugins": {
    "active-directory": {
      "buildDate": "Dec 13, 2021",
      "compatibleSinceVersion": "2.0",
      "dependencies": [
          "name": "mailer",
          "optional": false,
          "version": "1.5"
      "developers": [
          "developerId": "kohsuke",
          "name": "Kohsuke Kawaguchi"
          "developerId": "fbelzunc",
          "name": "Felix Belzunce Arcos"
      "excerpt": "Enables authentication through Active Directory",
      "gav": "org.jenkins-ci.plugins:active-directory:2.25.1",
      "labels": ["user"],
      "name": "active-directory",
      "releaseTimestamp": "2021-12-13T12:19:12.00Z",
      "requiredCore": "2.235.5",
      "scm": "",
      "sha1": "m19oZmHZSQFYtKDMQcb1zZMMJBQ=",
      "sha256": "iMvILkkm47x/rDw1RVkX8qSwymC2PedvkC5eMrvHZxY=",
      "title": "Jenkins Active Directory plugin",
      "url": "http://localhost:8080/job/Admin/job/CreateUpdateFile/ws/active-directory.hpi",
      "version": "2.25.1",
      "wiki": ""
  "updateCenterVersion": "1"

As the update-center.json file and the jenkins installation are local to the same machine, I see no reason to require a certificate to access the update-center.json file and so have omitted the ‘signature’ block. Only now I obviously get the following error when I click on the ‘Check Now’ button:

My question is, is there a way to disable the check for this signature block?? Prior to version 1.502, there was a boolean property called hudson.model.UpdateSite.signatureCheck that could be used …