Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...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_wheels.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-24.04
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Build wheels
         uses: pypa/cibuildwheel@v3.1.4
@@ -30,7 +30,7 @@ jobs:
     runs-on: ubuntu-24.04-arm
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Build wheels
         uses: pypa/cibuildwheel@v3.1.4
@@ -48,7 +48,7 @@ jobs:
     runs-on: macos-13
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Build wheels
         uses: pypa/cibuildwheel@v3.1.4
@@ -65,7 +65,7 @@ jobs:
     runs-on: macos-15
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Build wheels
         uses: pypa/cibuildwheel@v3.1.4
@@ -82,7 +82,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: '3.13'

.github/workflows/test-linux-build.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: '3.13'

.github/workflows/test-linux-cxx-only.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: '3.13'

.github/workflows/test-linux-dependencies.yml

@@ -28,7 +28,7 @@ jobs:
 
       - name: checkout libcasm-global
         if: steps.cache-libcasm-global-restore.outputs.cache-hit != 'true'
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: prisms-center/CASMcode_global
           path: CASMcode_global
@@ -62,7 +62,7 @@ jobs:
 
       - name: checkout libcasm-xtal
         if: steps.cache-libcasm-xtal-restore.outputs.cache-hit != 'true'
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: prisms-center/CASMcode_crystallography
           path: CASMcode_crystallography

.github/workflows/test-linux.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: '3.13'

.github/workflows/test-macos-build.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: macOS-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: '3.13'

.github/workflows/test-macos.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: macOS-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: '3.13'