Disable PREfast in Identitymodel pipeline (#62495)

Author: wtgodbe

.azure/pipelines/identitymodel-helix-matrix.yml

@@ -37,6 +37,8 @@ extends:
         compiled:
           enabled: false
           justificationForDisabling: 'This is a test-only pipeline. The same product code is already scanned in the main pipeline (aspnetcore-ci)'
+    featureFlags:
+      autoEnablePREfastWithNewRuleset: false
 
     stages:
     - stage: build