Update actions/checkout action to v4 (#4)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/c-cpp.yml

@@ -14,6 +14,6 @@ jobs:
     steps:
     - name: dependencies
       run: sudo apt-get install check imagemagick libtool-bin libmpc-dev libcairo2-dev libgd-dev libimlib2-dev
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: make
       run: make SILENT= LIBTOOL_SILENT=