Unpin ts-graphiz version in python-app.yml

Node.js is being installed as part of the graphviz setup, but then failing to run in a way that likely indicates it is out of date. This is likely because we are pinning the ts-graphviz action to an old version, and should unpin to use the latest instead.

.github/workflows/python-app.yml

@@ -39,7 +39,7 @@ jobs:
         python -m pip install pytest
         python -m pip install interrogate
     - name: Setup Graphviz
-      uses: ts-graphviz/setup-graphviz@v1
+      uses: ts-graphviz/setup-graphviz
     - name: Show Node.js version
       run: |
         node --version