Update ActiveIssue issue number

Author: stephentoub

src/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTest.ServerCertificates.cs

@@ -211,7 +211,7 @@ public async Task NoCallback_RevokedCertificate_RevocationChecking_Fails()
             new object[] { Configuration.Http.WrongHostNameCertRemoteServer , SslPolicyErrors.RemoteCertificateNameMismatch},
         };
 
-        [ActiveIssue(19793, TestPlatforms.Windows)]
+        [ActiveIssue(7812, TestPlatforms.Windows)]
         [OuterLoop] // TODO: Issue #11345
         [ConditionalTheory(nameof(BackendSupportsCustomCertificateHandling))]
         [MemberData(nameof(CertificateValidationServersAndExpectedPolicies))]