Remove unnecessary comma from docstring

Co-authored-by: Jim Bosch <[email protected]>

python/lsst/pex/config/configurableActions/_configurableActionField.py

@@ -49,7 +49,7 @@ class ConfigurableActionField(ConfigField[ActionTypeVar]):
     default : `lsst.pex.config.Config`, optional
         If default is `None`, the field will default to a default-constructed
         instance of ``dtype``. Additionally, to allow for fewer deep-copies,
-        assigning an instance of ``ConfigField`` to ``dtype`` itself, is
+        assigning an instance of ``ConfigField`` to ``dtype`` itself is
         considered equivalent to assigning a default-constructed sub-config.
         This means that the argument default can be ``dtype``, as well as an
         instance of ``dtype``.