bump checkout action

Author: tshepang

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
           - windows-latest
           - macOS-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v6
     - name: install ${{ matrix.rust }}
       run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
     - run: cargo build