Switch back to using the unofficial templates for PRs

They want us to split the PRs out into a separate pipeline that will have different capabilities (ie we can't sign from a PR pipeline). That needs to run on unofficial 1ES templates so the easiest way to do this is just add the conditional back.

Author: marcpopMSFT

.vsts-ci.yml

@@ -54,7 +54,10 @@ resources:
     ref: refs/tags/release
 
 extends:
-  template: v1/1ES.Official.PipelineTemplate.yml@1esPipelines
+  ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
+    template: v1/1ES.Official.PipelineTemplate.yml@1esPipelines
+  ${{ else }}:
+    template: v1/1ES.Unofficial.PipelineTemplate.yml@1esPipelines
   parameters:
     sdl:
       sourceAnalysisPool: