docs: Note pytest-doctest-docutils disabling of doctest module

Author: tony

README.md

@@ -76,6 +76,8 @@ $ python -m doctest_docutils README.md -v
 
 ### pytest plugin
 
+_This plugin disables pytest's standard `doctest` plugin._
+
 This plugin integrates with the above module.
 
 ```console

docs/doctest/pytest.md

@@ -1,5 +1,11 @@
 # pytest plugin
 
+:::{note}
+
+This plugin disables pytest's standard `doctest` plugin.
+
+:::
+
 The pytest plugin is built on top of the doctest_docutils module, which is in
 turn compatible with {mod}`doctest`.