ci: bump actions/checkout from 5 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...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

@@ -19,7 +19,7 @@ jobs:
     name: YAML lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v6
         with:
@@ -41,7 +41,7 @@ jobs:
       matrix:
         python-version: ["3.11", "3.12", "3.13"]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v6
         with:
@@ -59,7 +59,7 @@ jobs:
     name: Mutation testing
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v6
         with:
@@ -79,7 +79,7 @@ jobs:
     name: Python lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v6
         with:
@@ -105,7 +105,7 @@ jobs:
     # The script is what users run to produce a bug report, so it must work on
     # a stock system interpreter with nothing installed. macOS still ships 3.9.
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v6
         with:
@@ -138,7 +138,7 @@ jobs:
     name: Release metadata
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       # The version lives in the blueprint description and nowhere else, so it
       # can silently disagree with the changelog. A tag disagreeing with either
@@ -188,7 +188,7 @@ jobs:
     # here is a signal to investigate rather than a reason to block a merge.
     continue-on-error: true
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v6
         with:

.github/workflows/docs.yml

@@ -39,7 +39,7 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: actions/setup-python@v6
         with: