Uninstall vtk before install vtk-osmesa

Author: santisoler

.github/workflows/docs.yml

@@ -97,13 +97,14 @@ jobs:
           path: ~/conda_pkgs_dir
           key: conda-${{ runner.os }}-${{ env.PYTHON }}-${{ hashFiles('requirements-full.txt') }}
 
+      - name: Install requirements
+        run: conda install --quiet --file requirements-full.txt python=$PYTHON
+
       - name: Manually install vtk-osmesa from pip
         run: |
+          pip uninstall vtk vtk-base vtk-ffmpeg
           pip install vtk-osmesa --extra-index-url https://gitlab.kitware.com/api/v4/projects/13/packages/pypi/simple
 
-      - name: Install requirements
-        run: conda install --quiet --file requirements-full.txt python=$PYTHON
-
       - name: List installed packages
         run: conda list