Use preferred v3 checkout Action

Author: djdefi

.github/workflows/main.yml

@@ -24,7 +24,7 @@ jobs:
         brew install moreutils gawk
       if: matrix.os == 'macos-latest'
     - name: Get Sources
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
     - name: Test
       run: |
         export PATH="$PATH:/snap/bin"