CI: set editorconfig-checker version

To fix "Error: The binary 'ec-linux-amd64*' not found".

.github/workflows/cpp.yml

@@ -130,6 +130,10 @@ jobs:
 
     - name: Install editorconfig-checker
       uses: editorconfig-checker/action-editorconfig-checker@main
+      with:
+        # 'latest' v3.1.0 was missing binaries, so had to pin the version
+        # https://github.com/editorconfig-checker/editorconfig-checker/issues/409
+        version: v3.0.3
 
     - name: Check CMakeLists.txt formatting
       run: find . \( -name 'CMakeLists.txt' \) -exec editorconfig-checker {} \+ || { echo "EditorConfig check failed! See the README if you don't know how to fix this."; exit 1; }