DOC: leave doc requirements in one place

Author: Jacob-Stevens-Haas

.github/workflows/docs.yml

@@ -22,7 +22,7 @@ jobs:
         sudo apt-get update -y
         sudo apt-get install pandoc
         pip install -r examples/requirements.txt
-        pip install sphinx nbsphinx sphinx_rtd_theme
+        pip install -r requirements-docs.txt
     - name: Build docs
       run: |
         cd docs

requirements-docs.txt

@@ -1,3 +1,4 @@
 sphinx
 sphinx_rtd_theme
-nbsphinx
+nbsphinx
+ipython