Bump actions/checkout from 3 to 4 in /.github/workflows

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/Newsletter.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the MaCh3 repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0  # Fetch all history including tags
           repository: mach3-software/MaCh3
@@ -33,7 +33,7 @@ jobs:
           echo "current_date=${current_date}" >> $GITHUB_ENV
 
       - name: Checkout the MaCh3Tutorial repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0  # Fetch all history including tags
           repository: mach3-software/MaCh3Tutorial
@@ -53,7 +53,7 @@ jobs:
           echo "tutorial_latest_tag=${tutorial_latest_tag}" >> $GITHUB_ENV
 
       - name: Checkout the MaCh3-PythonUtils repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0  # Fetch all history including tags
           repository: mach3-software/MaCh3-PythonUtils