Update dependency sphinx_rtd_theme to v3 (#2089)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

requirements-doc.txt

@@ -57,7 +57,7 @@ sphinx-design==0.5.0
 sphinx_copybutton==0.5.2
 sphinx-notfound-page==1.0.0
 sphinx-tabs==3.4.5
-sphinx_rtd_theme==2.0.0
+sphinx_rtd_theme==3.0.1
 sphinxcontrib-applehelp==2.0.0
 sphinxcontrib-devhelp==2.0.0
 sphinxcontrib-htmlhelp==2.0.1