Update actions/checkout to v4

Author: jonasbb

.github/workflows/audit.yml

@@ -20,7 +20,7 @@ jobs:
     permissions:
       issues: write
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions-rust-lang/audit@working-directory
         name: Audit Rust Dependencies
         with:

.github/workflows/ci.yaml

@@ -8,7 +8,7 @@ jobs:
     name: cargo fmt
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
           toolchain: nightly
@@ -19,4 +19,4 @@ jobs:
           toolchain: stable
           components: clippy
       - uses: Swatinem/rust-cache@v2
-      - run: cargo clippy --all-targets --all-features --locked -- -D 
+      - run: cargo clippy --all-targets --all-features --locked -- -D