Update CI actions/setup-python from v4 to v5 which uses node20 (#100)

Author: adrianyorke

.github/workflows/main.yml

@@ -25,7 +25,7 @@ jobs:
         with:
           node-version: ${{ matrix.node-version }}
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies