build(deps): 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)
- [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] <[email protected]>

Author: dependabot[bot]

.github/workflows/main.yml

@@ -24,7 +24,7 @@ jobs:
       AFTER_INSTALL_TARGET_DEPENDENCIES: ./mavros/scripts/install_geographiclib_datasets.sh
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/cache@v4
         with:
           path: "${{ env.CCACHE_DIR }}"

.github/workflows/semgrep-analysis.yml

@@ -23,7 +23,7 @@ jobs:
     if: (github.actor != 'dependabot[bot]')
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: semgrep ci
         env:
           SEMGREP_RULES: p/default