Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/coreaudio-sys.yml

@@ -8,7 +8,7 @@ jobs:
       matrix:
         toolchain: [stable, nightly]
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: dtolnay/rust-toolchain@master
       with:
         toolchain: ${{ matrix.toolchain }}
@@ -26,7 +26,7 @@ jobs:
         toolchain: [stable, nightly]
         target: [aarch64-apple-ios, x86_64-apple-ios, aarch64-apple-ios-sim]
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: dtolnay/rust-toolchain@master
       with:
         toolchain: ${{ matrix.toolchain }}
@@ -43,7 +43,7 @@ jobs:
   macos-docs:
     runs-on: macOS-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: dtolnay/rust-toolchain@master
       with:
         toolchain: stable
@@ -58,7 +58,7 @@ jobs:
       CRATESIO_TOKEN: ${{ secrets.CRATESIO_TOKEN }}
     runs-on: macOS-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: dtolnay/rust-toolchain@master
       with:
         toolchain: stable