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/opencv-rust.yml

@@ -41,7 +41,7 @@ jobs:
       SCCACHE_GHA_ENABLED: "true"
       RUSTC_WRAPPER: "sccache"
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
       - uses: mozilla-actions/[email protected]
 
@@ -87,7 +87,7 @@ jobs:
       SCCACHE_GHA_ENABLED: "true"
       RUSTC_WRAPPER: "sccache"
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
       - uses: mozilla-actions/[email protected]
       - uses: actions/cache@v4
@@ -129,7 +129,7 @@ jobs:
       SCCACHE_GHA_ENABLED: "true"
       RUSTC_WRAPPER: "sccache"
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
       - uses: mozilla-actions/[email protected]
 
@@ -144,7 +144,7 @@ jobs:
   docs-rs:
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
 
       - name: Run a documentation generation test
@@ -158,7 +158,7 @@ jobs:
       SCCACHE_GHA_ENABLED: "true"
       RUSTC_WRAPPER: "sccache"
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: mozilla-actions/[email protected]
 
       - uses: actions/cache@v4