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] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -53,7 +53,7 @@ jobs:
 
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up stable toolchain
         if: github.event_name != 'schedule'
@@ -95,7 +95,7 @@ jobs:
 
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up stable toolchain
         uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -130,7 +130,7 @@ jobs:
 
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up toolchain
         uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -163,7 +163,7 @@ jobs:
 
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up toolchain
         uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -199,7 +199,7 @@ jobs:
 
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up toolchain
         uses: actions-rust-lang/setup-rust-toolchain@v1