Pin used python package versiosn in Github Actions

to the ones in conda_env/gdal-dev.yml

.github/workflows/tests.yml

@@ -20,9 +20,9 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install pylint
+          pip install pylint==2.15.*
           pip install mock
-          pip install requests
+          pip install requests==2.28.*
       - name: Analysing the code with pylint
         run: |
           pylint -j 0 ./wahoomc ./tests