Bump actions/checkout from 4 to 6 (#149)

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](https://github.com/actions/checkout/compare/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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/main.yml

@@ -24,7 +24,7 @@ jobs:
         run: cargo install cargo-audit
 
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Run cargo audit
         run: cargo audit -D warnings
@@ -47,7 +47,7 @@ jobs:
     name: test
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install ${{ matrix.toolchain }} toolchain
         uses: actions-rs/toolchain@v1
@@ -99,7 +99,7 @@ jobs:
           - --features danger
           - --features serde
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: hecrj/setup-rust-action@v2
       - run: rustup target add ${{ matrix.target }}
       - run: cargo build --verbose --target=${{ matrix.target }} --no-default-features ${{ matrix.frontend_feature }} ${{ matrix.backend_feature }}
@@ -110,7 +110,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install stable toolchain
         uses: actions-rs/toolchain@v1
@@ -140,7 +140,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install nightly toolchain
         uses: actions-rs/toolchain@v1
@@ -173,7 +173,7 @@ jobs:
         run: cargo install taplo-cli --locked
 
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Run Taplo
         run: taplo fmt --check