doc: tomli is not needed for Python >= 3.11 (#2751)

README.rst

diff --git a/README.rst b/README.rst
index 5399c77..d9d15f4 100644
--- a/README.rst
+++ b/README.rst
@@ -135,8 +135,8 @@
 
 Codespell will also check in the current directory for a ``pyproject.toml``
 (or a path can be specified via ``--toml <filename>``) file, and the
-``[tool.codespell]`` entry will be used as long as the tomli_ package
-is installed, for example:
+``[tool.codespell]`` entry will be used, but only if the tomli_ package
+is installed for versions of Python prior to 3.11. For example:
 
 .. code-block:: toml