added clarifying comment

Signed-off-by: evanchia <evanchia@amazon.com>

scripts/build/Jenkins/Jenkinsfile

@@ -471,7 +471,7 @@ def PostBuildCommonSteps(String workspace, Map params, boolean mount = true) {
         dir([workspace, ENGINE_REPOSITORY_NAME, params.OUTPUT_DIRECTORY].join('/')){
             // Clean up Testing directory
             palRmDir("Testing")
-            // Recreate test runner xml directories that need to be pre generated
+            // Recreate test runner xml directories that need to be pre generated to prevent race condition on incremental runs
             palMkdir("Testing/Pytest")
             palMkdir("Testing/Gtest")
         }