Corrected docs and removed unused code for got_request_exception signal's sender argument.

Inaccurate since 7d1b69dbe7.

django/core/handlers/exception.py

@@ -102,12 +102,12 @@ def response_for_exception(request, exc):
     return response
 
 
-def get_exception_response(request, resolver, status_code, exception, sender=None):
+def get_exception_response(request, resolver, status_code, exception):
     try:
         callback, param_dict = resolver.resolve_error_handler(status_code)
         response = callback(request, **{**param_dict, 'exception': exception})
     except Exception:
-        signals.got_request_exception.send(sender=sender, request=request)
+        signals.got_request_exception.send(sender=None, request=request)
         response = handle_uncaught_exception(request, resolver, sys.exc_info())
 
     return response

docs/ref/signals.txt

@@ -547,7 +547,7 @@ This signal is sent whenever Django encounters an exception while processing an
 Arguments sent with this signal:
 
 ``sender``
-    The handler class, as above.
+    Unused (always ``None``).
 
 ``request``
     The :class:`~django.http.HttpRequest` object.