Update actions/checkout action to v6 (#155)

Co-authored-by: oxide-renovate[bot] <146848827+oxide-renovate[bot]@users.noreply.github.com>

Author: oxide-renovate[bot]

.github/workflows/rust.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6
 
       - uses: dtolnay/rust-toolchain@master
         with: