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/check-release-notes.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 1
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Default MISSING_CHANGELOG_ENTRY to 1
         run: echo 'MISSING_CHANGELOG_ENTRY=1' >> "$GITHUB_ENV"

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 6
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ./.github/actions/setup-python
         with:
           python-version: "3.10"
@@ -66,7 +66,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     timeout-minutes: 8
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           # TODO: This can be very expensive for large repos. Is there a better way to do this?
           # Fetch all history and tags for setuptools_scm to work

.github/workflows/codeql.yml

@@ -29,7 +29,7 @@ jobs:
       # actions: read
       # contents: read
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - uses: github/codeql-action/init@v4
       with:

.github/workflows/release.yml

@@ -32,7 +32,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 6
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           # TODO: This can be very expensive for large repos. Is there a better way to do this?
           # Fetch all history and tags for setuptools_scm to work
@@ -105,7 +105,7 @@ jobs:
     steps:
 
       # Generate the release notes
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           # TODO: This can be very expensive for large repos. Is there a better way to do this?
           # Fetch all history and tags for setuptools_scm to work