Bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -20,7 +20,7 @@ jobs:
         python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           fetch-depth: 1
       - name: Install Go

.github/workflows/conformance.yaml

@@ -20,7 +20,7 @@ jobs:
         python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           fetch-depth: 1
       - name: Install Go

.github/workflows/release.yaml

@@ -12,7 +12,7 @@ jobs:
       name: release
     steps:
       - name: Checkout source
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           fetch-depth: 0
       - name: Set VERSION variable from tag
@@ -39,7 +39,7 @@ jobs:
     needs: build
     steps:
       - name: Checkout source
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           fetch-depth: 0