Update actions/checkout in GitHub Actions to v4 (#57, thanks @striezel)

Author: striezel

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Install GCC ${{ matrix.version }}
         run: sudo apt-get install -y gcc-${{ matrix.version }} g++-${{ matrix.version }}
@@ -52,7 +52,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Install Clang ${{ matrix.version }}
         run: sudo apt-get install -y clang-${{ matrix.version }}
@@ -83,7 +83,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Configure tests
         run: cmake -S . -B build