Disable testRemoteUpdateSitePerformingValidation temporarily (#26342)

The certificate in the test source code expired Feb 20, 2026 and I was
unable to find the correct steps to regenerate the certificate and the
matching platform-plugins.json file.

Rather than block other pull requests because the test is failing on
the master branch, let's disable the test.

Testing done:

* Confirmed that the test fails without this change
* Confirmed that the test passes with this change
* Attempted to create a new certificate as demo.crt based on the comments
  at the end of the source file, but was unable to create the correct
  platform-plugin.json file to use the new demo.crt

Author: MarkEWaite

test/src/test/java/jenkins/install/SetupWizardTest.java

@@ -64,6 +64,7 @@
 import org.htmlunit.html.HtmlPage;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
 import org.jvnet.hudson.test.Issue;
@@ -273,6 +274,7 @@ void testRemoteUpdateSiteSkippingValidation() throws Exception {
         }
     }
 
+    @Disabled("TODO Test certificate needs to be recreated, expired 2026-02-20")
     @Test
     void testRemoteUpdateSitePerformingValidation() throws Exception {
         URL baseUrl;