Update dotnet-code-metrics.yml (#7032)

use forked version of GHA to reduce security surface area. similar to https://github.com/dotnet/aspire/pull/8122/files

Author: danmoseley

.github/workflows/dotnet-code-metrics.yml

@@ -41,7 +41,7 @@ jobs:
         dir: ${{ './github-actions/DotNet.GitHubAction' }}
 
     - name: Create pull request
-      uses: peter-evans/create-pull-request@v7.0.8
+      uses: dotnet/actions-create-pull-request@v4
       if: ${{ steps.dotnet-code-metrics.outputs.updated-metrics }} == 'true'
       with:
         title: '${{ steps.dotnet-code-metrics.outputs.summary-title }}'