lintreadme: the README is ReST, not Markdown

Author: mr-c

tox.ini

@@ -55,7 +55,7 @@ deps =
   py311-pydocstyle: diff-cover
   py311-lintreadme: twine
   py311-lintreadme: build
-  py311-lintreadme: readme_renderer[md]
+  py311-lintreadme: readme_renderer[rst]
 
 setenv =
   py3{6,7,8,9,10,11}-unit: LC_ALL = C.UTF-8