Avoid installing unused tools in CI environment

CairoSVG is not required in CI environment. Installing it is useless overhead.

Go with latest available "black" to check python code formatting.

.github/workflows/ci.yaml

@@ -14,8 +14,8 @@ jobs:
       with:
         python-version-file: '.python-version'
 
-    - name: Install dependencies
-      run: python -m pip install -U -r requirements-dev.txt
+    - name: Install Black
+      run: python -m pip install -U black
 
     - name: Check formatting
       run: python -m black --check .