ensure tox.ini is also updated with new req

Author: scbedd

eng/tox/tox.ini

@@ -329,6 +329,7 @@ deps =
   sphinx_rtd_theme==3.0.2
   myst_parser==4.0.1
   sphinxcontrib-jquery==4.1
+  sphinxcontrib-mermaid==1.0.0
 commands =
   python {repository_root}/eng/tox/create_package_and_install.py \
     -d {envtmpdir}/dist \