github-actions: update test jobs

Author: MartinBubel

.github/workflows/test.yml

@@ -27,13 +27,16 @@ jobs:
         with:
           python-version: ${{ matrix.python }}
 
+      - name: Install dependencies
+        run: |
+          pip install setuptools
+          pip install matplotlib
+          pip install pytest
+      
       - name: Install lib
         run: |
-          pip install --upgrade pip
-          pip install -e .
+          python setup.py develop
 
       - name: pytest
         run: |
-          pip install matplotlib
-          pip install pytest
           pytest GPy/testing