GitHub Action: Bump actions/checkout from 4 to 6 (#1581)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to
6.

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/backport-to-release-branch.yml

@@ -49,7 +49,7 @@ jobs:
         private-key: ${{ secrets.MU_ACCESS_APP_PRIVATE_KEY }}
 
     - name: Checkout code
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         token: ${{ steps.app-token.outputs.token }}

.github/workflows/release-basetools.yml

@@ -48,7 +48,7 @@ jobs:
 
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Setup Python
         uses: actions/setup-python@v5
@@ -102,7 +102,7 @@ jobs:
 
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Download Artifacts
         uses: actions/download-artifact@v6

.github/workflows/update-basetools.yml

@@ -120,7 +120,7 @@ jobs:
 
       - name: Checkout Code
         if: steps.pr-check.outputs.exists != 'true'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ env.BRANCH_NAME }}