ci: Update build suffix for mock builds

.ci/templates/build-mock.yml

@@ -1,5 +1,5 @@
 steps:
   - script: mkdir artifacts || echo 'X' > artifacts/T1.txt
   - publish: artifacts
-    artifact: 'yuzu-$(BuildName)-$(BuildSuffix)'
+    artifact: 'yuzu-$(BuildName)-mock'
     displayName: 'Upload Artifacts'