Adopt new Sphinx theme name

docs/doc-requirements.txt

@@ -3,4 +3,4 @@
 sphinx>=1.4, !=1.5.4
 recommonmark
 sphinxcontrib-autoprogram
-git+https://github.com/pandas-dev/pandas-sphinx-theme.git@master
+pydata-sphinx-theme

docs/source/conf.py

@@ -117,7 +117,7 @@ html_favicon = "_static/images/favicon.ico"
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 #
-html_theme = "pandas_sphinx_theme"
+html_theme = "pydata_sphinx_theme"
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the