clean up doc dir (AtsushiSakai#568)

* clean up doc dir

* clean up doc dir

* clean up doc dir

* clean up doc dir

Author: AtsushiSakai

.circleci/config.yml

@@ -12,7 +12,7 @@ jobs:
       - python/load-cache
       - python/install-deps
       - python/save-cache
-      - run: pip install sphinx sphinx-autobuild sphinx-rtd-theme pytest IPython
+      - run: pip install -r requirements.txt
       - run:
           command: cd docs;make html
           name: doc_build

requirements.txt

@@ -5,5 +5,6 @@ matplotlib == 3.4.3
 cvxpy == 1.1.17
 pytest == 6.2.5 # For unit test
 pytest-xdist == 2.4.0 # For unit test
-sphinx == 4.3.0 # For sphinx documentation
+sphinx < 4.0 # For sphinx documentation
+sphinx_rtd_theme == 1.0.0
 IPython == 7.29.0 # For sphinx documentation