Bump actions/checkout from 5.0.0 to 6.0.0 (#530)

Bumps [actions/checkout](https://github.com/actions/checkout) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/checks.yaml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out code from GitHub
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6.0.0
         with:
           fetch-depth: 2
       - name: Set up Python 3.13

.github/workflows/primer.yaml

@@ -12,11 +12,11 @@ jobs:
     permissions: write-all
     steps:
       - name: Check out working version
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6.0.0
         with:
           fetch-depth: 2
       - name: Check out changeable version
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6.0.0
         with:
           path: program_to_test
           fetch-depth: 0

.github/workflows/publish.yaml

@@ -14,7 +14,7 @@ jobs:
       id-token: write
     steps:
       - name: Check out code from GitHub
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6.0.0
       - name: Set up Python 3.x
         uses: actions/setup-python@v6
         with:

.github/workflows/tests.yaml

@@ -16,7 +16,7 @@ jobs:
         python-version: [3.9, "3.10", "3.11", "3.12", "3.13"]
     steps:
       - name: Check out code from GitHub
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6.0.0
       - name: Set up Python ${{ matrix.python-version }}
         id: python
         uses: actions/setup-python@v6
@@ -42,7 +42,7 @@ jobs:
         python-version: [3.9, "3.10", "3.11", "3.12", "3.13"]
     steps:
       - name: Check out code from GitHub
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6.0.0
       - name: Set temp directory
         run: echo "TEMP=$env:USERPROFILE\AppData\Local\Temp" >> $env:GITHUB_ENV
         # Workaround to set correct temp directory on Windows
@@ -69,7 +69,7 @@ jobs:
     needs: ["tests-linux", "tests-windows"]
     steps:
       - name: Check out code from GitHub
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6.0.0
       - name: Set up Python 3.11
         id: python
         uses: actions/setup-python@v6