updated gitlab-ci to install requirements before building the documentation....

I believe the problem with autodoc constructing the documentation was caused by missing dependencies. This merge request install all pyicon dependencies before attempting to build the documentation.

ci/requirements_py311.yml

+name: pyicon_py311
+channels:
+  - conda-forge
+dependencies:
+  - python=3.11
+  - numpy
+  - dask
+  - matplotlib
+  - cartopy
+  - netcdf4
+  - xarray
+  - zarr
+  - pandas
+  - cmocean
+  - scipy
+  - ipdb
+  - ipywidgets
+  - jupytext
+  - pytest
+  - healpy
+  - pandoc
+  - sphinx  # Documentation
+  - nbsphinx  # Documentation
+  - nbsphinx-link  # Documentation
+  - sphinx-copybutton  # Documentation
+  - pydata-sphinx-theme  # Documentation