build(deps): bump actions/checkout from 5 to 6 (#589)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
       fail-fast: false
     steps:
       - name: Checkout branch
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install linux only test dependency
         if: matrix.os == 'ubuntu-latest'
         # Install all dependencies needed to run Qt on linux (taken from the qt website)

.github/workflows/docs.yml

@@ -21,7 +21,7 @@ jobs:
     name: Docs building
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Get history and tags for SCM versioning to work
         run: |
           git fetch --prune --unshallow

.github/workflows/release.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Get history and tags for SCM versioning to work
         run: |
           git fetch --prune --unshallow
@@ -47,7 +47,7 @@ jobs:
         os: [windows-latest, ubuntu-latest, macos-latest]
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Get history and tags for SCM versioning to work
         run: |
           git fetch --prune --unshallow