Update a string value in Get PR Changed Files Script (Azure#26637)

* Update get-pr-changed-files.yml

* Update get-pr-changed-files.yml

Author: YanaXu

.azure-pipelines/util/get-pr-changed-files.yml

@@ -7,13 +7,13 @@ steps:
     script: |
       # refer to https://learn.microsoft.com/azure/devops/pipelines/build/variables?view=azure-devops&tabs=yaml#system-variables-devops-services
       # get the target branch name
-      $targetBranch = $(System.PullRequest.TargetBranch)
+      $targetBranch = "$(System.PullRequest.TargetBranch)"
       # fetch the targetBranch from origin to local branch and rename the branch to 'origin/base'
       git fetch --no-tags origin "${targetBranch}:origin/base"
       # refer to https://git-scm.com/docs/git-diff
       # compare the pr and targetBranch branch, get the changed file list
-      # diff-filter options are ACMRT, which are: Added, Copied, Modified, Renamed , Changed
-      $changedFiles = git --no-pager diff --name-only --diff-filter=ACMRT origin/base -- .
+      # diff-filter options are ACDMRT, which are: Added, Copied, Deleted, Modified, Renamed, Changed
+      $changedFiles = git --no-pager diff --name-only --diff-filter=ACDMRT origin/base -- .
       Write-Host "Total updated files:" $changedFiles.Count
       Write-Host "All Updated files:"
       $changedFiles | Foreach-Object {Write-Host $_}