build(deps): bump actions/checkout from 5 to 6 (#1370)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
   rustfmt:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt
@@ -50,7 +50,7 @@ jobs:
       image: tamasfe/taplo:0.8.1
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: taplo lint
         run: taplo lint
       - name: taplo fmt
@@ -59,7 +59,7 @@ jobs:
   clippy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: 'recursive'
       - name: install protoc
@@ -83,7 +83,7 @@ jobs:
   docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: 'recursive'
       - name: install protoc
@@ -102,7 +102,7 @@ jobs:
   machete:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
       - uses: taiki-e/install-action@cargo-machete
       - name: Check unused dependencies
@@ -111,7 +111,7 @@ jobs:
   unused_dependencies:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: 'recursive'
       - uses: dtolnay/rust-toolchain@nightly
@@ -139,7 +139,7 @@ jobs:
           - macos-14
           - windows-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: 'recursive'
       - name: install toolchain (${{ matrix.toolchain }})
@@ -161,7 +161,7 @@ jobs:
   msrv:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: install protoc
         uses: taiki-e/install-action@v2
         with:
@@ -176,7 +176,7 @@ jobs:
   minimal-versions:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@nightly
       - uses: dtolnay/rust-toolchain@stable
       - uses: taiki-e/install-action@cargo-hack
@@ -186,7 +186,7 @@ jobs:
   kani:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Verify with Kani
         uses: model-checking/kani-github-action@v1.1
         with:
@@ -195,7 +195,7 @@ jobs:
   no-std:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@nightly
       - name: install protoc
         uses: taiki-e/install-action@v2
@@ -223,15 +223,15 @@ jobs:
   semver-checks:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Check semver
         uses: obi1kenobi/cargo-semver-checks-action@v2
 
   check-readme:
     name: Check README
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Verify that Prost version is up to date in README
         run: grep -q "$(sed '/^version = /!d' Cargo.toml | head -n1)" README.md
       - name: Verify that MSRV version is up to date in README