Update renderers documentation example (#9362)

docs/api-guide/renderers.md

@@ -283,7 +283,7 @@ By default this will include the following keys: `view`, `request`, `response`,
 
 The following is an example plaintext renderer that will return a response with the `data` parameter as the content of the response.
 
- from django.utils.encoding import smart_text
+ from django.utils.encoding import smart_str
  from rest_framework import renderers
 
 
@@ -292,7 +292,7 @@ The following is an example plaintext renderer that will return a response with
   format = 'txt'
 
   def render(self, data, accepted_media_type=None, renderer_context=None):
-  return smart_text(data, encoding=self.charset)
+  return smart_str(data, encoding=self.charset)
 
 ## Setting the character set