Fixed #21339 -- Documented removal of some form field error messages

docs/releases/1.6.txt

@@ -830,6 +830,14 @@ Miscellaneous
   changes in 1.6 particularly affect :class:`~django.forms.DecimalField` and
   :class:`~django.forms.ModelMultipleChoiceField`.
 
+* Some :attr:`~django.forms.Field.error_messages` for
+  :class:`~django.forms.IntegerField`,
+  :class:`~django.forms.EmailField`,
+  :class:`~django.forms.IPAddressField`,
+  :class:`~django.forms.GenericIPAddressField`, and
+  :class:`~django.forms.SlugField` have been suppressed because they
+  duplicated error messages already provided by validators tied to the fields.
+
 * There have been changes in the way timeouts are handled in cache backends.
   Explicitly passing in ``timeout=None`` no longer results in using the
   default timeout. It will now set a non-expiring timeout. Passing 0 into the