Install latest PennyLane for CI (#110)

.github/workflows/tests.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.9, '3.10', '3.11']
+        python-version: ['3.9', '3.10', '3.11']
 
     steps:
       - name: Cancel Previous Runs
@@ -26,6 +26,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install -r requirements.txt
+          pip install --upgrade git+https://github.com/PennyLaneAI/pennylane.git#egg=pennylane
           pip install wheel pytest pytest-cov pytest-mock pytest-benchmark --upgrade
       - name: Install Plugin
         run: |
@@ -62,6 +63,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install -r requirements.txt
+          pip install --upgrade git+https://github.com/PennyLaneAI/pennylane.git#egg=pennylane
           pip install wheel pytest pytest-benchmark pytest-cov pytest-mock flaky --upgrade
 
       - name: Install Plugin