Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v3...v4)

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

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ccpp.yml

@@ -46,7 +46,7 @@ jobs:
             toolchain: ninja-vs-win64-cxx17
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
           submodules: true
           
@@ -69,7 +69,7 @@ jobs:
 
     - name: Checkout Hunter toolchains
       if: endsWith(matrix.name, 'hunter')
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         repository: cpp-pm/polly
         path: cmake/polly