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)
- [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] <[email protected]>

Author: dependabot[bot]

.github/workflows/doc_checks.yml

@@ -24,7 +24,7 @@ jobs:
     container: ghcr.io/osgeo/proj-docs
 
     steps:
-    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v4.1.7
+    - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v4.1.7
 
     - name: Update sphinx-rtd-theme
       shell: bash -l {0}

.github/workflows/emscripten.yml

@@ -24,7 +24,7 @@ jobs:
     if: "!contains(github.event.head_commit.message, '[ci skip]') && !contains(github.event.head_commit.message, '[skip ci]')"
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Build docker
         run: docker build -t proj-emscripten-builder scripts/ci/emscripten/