Bump actions/checkout from 3 to 4

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](https://github.com/actions/checkout/compare/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/CI.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: 'Checkout kubuntuJammy Repo'
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Get version
         run: |
@@ -19,7 +19,7 @@ jobs:
          echo "release=${REL}" >> $GITHUB_ENV
           
       - name: 'Checkout kubuntuMainline Repo'
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: kubuntuMainline
           persist-credentials: false
@@ -41,7 +41,7 @@ jobs:
   ISO:
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Build
         run: sudo ./build_in_docker.sh