build: eventlet 0.33.3 says they fixed the problem

Author: nedbat

tox.ini

@@ -29,9 +29,6 @@ setenv =
     # For some tests, we need .pyc files written in the current directory,
     # so override any local setting.
     PYTHONPYCACHEPREFIX=
-    # https://github.com/rthalley/dnspython/issues/885
-    # https://github.com/eventlet/eventlet/issues/781
-    EVENTLET_NO_GREENDNS=yes
 
 commands =
     # Create tests/zipmods.zip