Try to fix gitlab CI Pyimport error with Conda.jl

.gitlab-ci.yml

@@ -20,6 +20,7 @@ pages:
     - export PYTHON="" 
       # The Pkg.develop() makes MarkovProcesses.jl available in julia
     - julia --project=docs/ -e 'using Pkg; Pkg.develop(PackageSpec(path=".")); Pkg.instantiate();'
+    - julia --project=docs/ -e 'using Pkg; Pkg.add("Conda"); using Conda; Conda.add("python=3.9"); Conda.add("scikit-learn")'
     - julia --project=docs/ --color=yes docs/make.jl  # make documentation
     - mkdir public
     # - mkdir public/dev