Bump version of actions (#55)

actions/setup-python@v4 to avoid deprecation warnings

Author: dmdunla

.github/workflows/regression-tests.yml

@@ -21,7 +21,7 @@ jobs:
     steps:
     - uses: actions/checkout@v3
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies