Update testing workflow to install AG2

Signed-off-by: Mark Sze <mark@sze.family>

.github/workflows/contrib-tests.yml

@@ -755,6 +755,9 @@ jobs:
         run: |
           python -m pip install --upgrade pip wheel
           pip install pytest-cov>=5
+      - name: Install packages and dependencies for Swarms
+        run: |
+          pip install -e .
       - name: Set AUTOGEN_USE_DOCKER based on OS
         shell: bash
         run: |