Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/build-ij1.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: 'ubuntu-latest'
     steps:
       - name: Checkout branch ${{ github.ref_name }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:

.github/workflows/build-ij2.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: 'ubuntu-latest'
     steps:
       - name: Checkout branch ${{ github.ref_name }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:

.github/workflows/build-matlab.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: 'ubuntu-latest'
     steps:
     - name: Checkout branch ${{ github.ref_name }}
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
     - name: Setup MATLAB
       uses: matlab-actions/setup-matlab@v2
     - name: Run build

.github/workflows/publish-java.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: 'ubuntu-latest'
     steps:
       - name: Checkout branch ${{ github.ref_name }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Set up JDK
         uses: actions/setup-java@v4
         with: