Allow aio molecule env use ATMOSPHERE_DEBUG

ATMOSPHERE_DEBUG is default to false anyway, so this
change affects no one.

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Change-Id: Ic013b51b8a43c57545a83edd33eafe12eace39f7
diff --git a/tox.ini b/tox.ini
index fa730ed..66becf5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -66,7 +66,6 @@
 deps =
   {[testenv:molecule-venv]deps}
 setenv =
-  ATMOSPHERE_DEBUG = false
   openvswitch: ATMOSPHERE_NETWORK_BACKEND = openvswitch
   ovn: ATMOSPHERE_NETWORK_BACKEND = ovn
 commands =