Install fewer packages

Author: seisman

.github/workflows/continuous-documentation.yml

@@ -33,7 +33,10 @@ jobs:
 
       - name: Install dependencies
         shell: bash -l {0}
-        run: conda env update --file environment.yml
+        run: |
+          conda install gmt=6.1.1 numpy pandas xarray netcdf4 packaging \
+                        ipython myst-parser sphinx sphinx-copybutton \
+                        sphinx-gallery sphinx_rtd_theme=0.4.3
 
       - name: List installed packages
         shell: bash -l {0}