fix(ci): Install pip dependencies in pylint job

.github/workflows/pylint.yml

@@ -18,6 +18,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install pylint
+        pip install -r backend/requirements.txt
     - name: Analysing the code with pylint
       run: |
         pylint $(git ls-files '*.py')