Bump actions/checkout from 2 to 4 (#109)

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -43,7 +43,7 @@ jobs:
             binary_target: x86_64-unknown-linux-gnu
             toolchain: 1.62.1
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           submodules: recursive
       - uses: davidB/rust-cargo-make@v1