Bump actions/checkout from 6 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
 
     steps:
       - name: Checkout Repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v6

.github/workflows/publish.yml

@@ -32,7 +32,7 @@ jobs:
       id-token: write
     steps:
       - name: Checkout Repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Set up oldest tested Python
         uses: actions/setup-python@v6

.github/workflows/supply-chain.yml

@@ -32,7 +32,7 @@ jobs:
           - '3.14'
 
     steps:
-    - uses: actions/checkout@v6
+    - uses: actions/checkout@v7
       with:
         # This enables supply chain review against only a selected
         # branch.  For those using the "Git-Flow" style of branching,