remove eventlet from requirements

we don't depend on eventlet, we shouldn't have it in requirements

Change-Id: Ifee667a3e1a5b2ffe4f87d3fe28f639494785bfc
diff --git a/requirements.txt b/requirements.txt
index cd11aa7..e070549 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -18,7 +18,6 @@
 keyring>=1.6.1,<2.0
 testrepository>=0.0.17
 oslo.config>=1.2.0
-eventlet>=0.13.0
 six>=1.4.1
 iso8601>=0.1.8
 fixtures>=0.3.14