Fix docs typo (#7387)

Author: loingo95

docs/api-guide/fields.md

@@ -595,7 +595,7 @@ If you want to create a custom field, you'll need to subclass `Field` and then o
 
 The `.to_representation()` method is called to convert the initial datatype into a primitive, serializable datatype.
 
-The `to_internal_value()` method is called to restore a primitive datatype into its internal python representation. This method should raise a `serializers.ValidationError` if the data is invalid.
+The `.to_internal_value()` method is called to restore a primitive datatype into its internal python representation. This method should raise a `serializers.ValidationError` if the data is invalid.
 
 ## Examples