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] <[email protected]>

Author: dependabot[bot]

.github/workflows/release-to-pypi.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
 
     - name: Check out the release commit
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v5
@@ -43,7 +43,7 @@ jobs:
     steps:
 
     - name: Check out the release commit
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v5

.github/workflows/run-core-traits-tests.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with:

.github/workflows/run-style-checks.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up Python 3.10
       uses: actions/setup-python@v5
       with:

.github/workflows/run-traits-tests.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with:

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

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up Python 3.10
       uses: actions/setup-python@v5
       with: