Bump actions/checkout from 3 to 4 (#935)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to
4.
- [Release notes](https://github.com/actions/checkout/releases)
-
[Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

.github/workflows/rustfmt.yml

@@ -21,7 +21,7 @@ jobs:
   format:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: dtolnay/rust-toolchain@nightly
         with:
@@ -30,4 +30,4 @@ jobs:
       - uses: LoliGothick/rustfmt-check@master
         with:
           token: ${{ github.token }}
-          working-directory: userspace/ksud
+          working-directory: userspace/ksud