remove get_html_theme_path because it's deprecated

docs/conf.py

@@ -370,10 +370,7 @@ def jupyter_notebook(script_blocks, gallery_conf, target_dir, real_func):
 on_rtd = os.environ.get("READTHEDOCS", None) == "True"
 # only import rtd theme and set it if want to build docs locally
 if not on_rtd and html_theme == "rtd":
-    import sphinx_rtd_theme
-
     html_theme = "sphinx_rtd_theme"
-    html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,