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] <support@github.com>

Author: dependabot[bot]

.github/workflows/benches.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: HPKE Benchmarks
       run: cargo bench manual_benches
     - name: HPKE Rust Crypto Benchmarks

.github/workflows/coverage.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - uses: dtolnay/rust-toolchain@nightly
         with:

.github/workflows/ios.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: macos-13
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Setup MacOS
       run: |
         rustup target install aarch64-apple-darwin

.github/workflows/rust.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Run tests all features
       run: cargo test --verbose --no-default-features --all-features
       # Release
@@ -78,7 +78,7 @@ jobs:
           - target: aarch64-apple-ios
             rust: stable
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: ${{ matrix.rust }}
@@ -96,7 +96,7 @@ jobs:
           - ubuntu-latest
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install latest nightly
         uses: dtolnay/rust-toolchain@stable
         with:
@@ -111,7 +111,7 @@ jobs:
   no-std-check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       # we use a target that lacks a pre-compiled libstd to check if any dependency is using libstd
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable