Update python-app.yml

Use latest GitHub actions:
- https://github.com/marketplace/actions/setup-python
- https://github.com/marketplace/actions/setup-graphviz

and greatly simplify the installation on Windows.

.github/workflows/python-app.yml

@@ -26,7 +26,7 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Set up Python 3.8
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v5
       with:
         python-version: 3.8
 
@@ -76,7 +76,7 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Set up Python 3.8
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v5
       with:
         python-version: 3.8
 
@@ -85,41 +85,14 @@ jobs:
         python -m pip install --upgrade pip
         pip install wheel
 
-    - name: Install graphviz for visualization test
-      if: ${{ runner.os == 'macOS' }}
+    - name: Setup Graphviz
       uses: ts-graphviz/setup-graphviz@v2
       with:
         macos-skip-brew-update: 'true' # default false
 
-    - name: Setup Conda
-      if: ${{ runner.os == 'Windows' }}
-      uses: s-weigand/setup-conda@v1
-      with:
-        # Whether to activate the conda base env (Default: 'true')
-        activate-conda: true
-        # Python version which should be installed with conda (default: 'Default')
-        python-version: 3.8
-
-    - name: Install graphviz via conda
-      if: ${{ runner.os == 'Windows' }}
-      run: |
-        conda install -c anaconda graphviz
-
-    - name: add graphviz PATH
-      if: ${{ runner.os == 'Windows' }}
-      run: |
-        # should give base conda python
-        $python=Get-Command python
-        $pypath=Split-Path $python.Source -Parent
-        # Add to PATH, we know pypath is on it
-        $dot=[IO.Path]::Combine($pypath, 'Library', 'bin', 'graphviz')
-        echo $dot | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
-      shell: powershell
-
     - name: register plugins for graphviz
       if: ${{ runner.os == 'Windows' }}
       run: |
-        # execute dot
         dot -V
         dot -c