Install GeNN in test workflow

.github/workflows/testsuite.yml

@@ -46,9 +46,18 @@ jobs:
           activate-environment: 'test_env'
           python-version: ${{ matrix.python-version }}
 
+      - name: Install GeNN
+        run: |
+          # clone GeNN from github
+          git clone --depth=1 --no-single-branch https://github.com/genn-team/genn.git ../genn
+          cd ../genn
+          echo "GENN_PATH=$(pwd)" >> "$GITHUB_ENV"
+          # switch to stable release
+          git checkout 4.8.0
+
       - name: Install Brian2 and dependencies
         run: |
-          conda install -n test_env --quiet --yes -c conda-forge pip pytest cython sympy future pyparsing numpy jinja2 six scipy sphinx gsl coverage
+          conda install -n test_env --quiet --yes -c conda-forge pip pytest cython sympy pyparsing numpy jinja2 scipy sphinx
           pip install .
 
       - name: Run Tests