pytest workflow cleaned up

.github/workflows/pytest.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "pypy3"]
+        python-version: ["3.6", "3.7", "3.8", "3.9"]
 
     steps:
       - name: Checkout source
@@ -27,12 +27,6 @@ jobs:
       - name: Install
         run: |
           python -m pip install --upgrade pip
-          pip install numpy>=1.16
-          pip install scipy
-          pip install autograd>=1.2
-          pip install numdifftools
-          pip install matplotlib
-          pip install iminuit<2
           pip install .
           pip install pytest
           pip install pytest-cov