chore(deps): update actions/checkout action to v6 (#123)

Signed-off-by: bootc-bot[bot] <225049296+bootc-bot[bot]@users.noreply.github.com>
Co-authored-by: bootc-bot[bot] <225049296+bootc-bot[bot]@users.noreply.github.com>

Author: bootc-bot[bot]

.github/workflows/ci.yaml

@@ -21,7 +21,7 @@ jobs:
     name: Semver Checks
     runs-on: ubuntu-24.04
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: obi1kenobi/cargo-semver-checks-action@v2
       with:
         # Pinned until cargo-semver-checks supports rustdoc format v57 (Rust 1.93+)