DOC: Add note about TOML regex; fix typo (#552)

Add note about TOML regex; fix typo

Author: stefmolin

doc/validation.rst

@@ -33,7 +33,7 @@ the pre-commit hook as follows:
   ``ES01`` (using the same logic as the :ref:`validation during Sphinx build
   <validation_during_sphinx_build>` for ``numpydoc_validation_checks``).
 * ``exclude``: Don't report issues on objects matching any of the regular
-  regular expressions ``\.undocumented_method$`` or ``\.__repr__$``. This
+  expressions ``\.undocumented_method$`` or ``\.__repr__$``. This
   maps to ``numpydoc_validation_exclude`` from the
   :ref:`Sphinx build configuration <validation_during_sphinx_build>`.
 * ``override_SS05``: Allow docstrings to start with "Process ", "Assess ",
@@ -52,6 +52,7 @@ the pre-commit hook as follows:
         "SA01",
         "ES01",
     ]
+    # remember to use single quotes for regex in TOML
     exclude = [  # don't report on objects that match any of these regex
         '\.undocumented_method$',
         '\.__repr__$',