remove six in test requirements since it is already in main requirements

xinyzhou · xinyzhou · commit 0c9a4c3e8141 · 2019-09-26T20:55:34.000-07:00
diff --git a/tests/test-requirements.txt b/tests/test-requirements.txt
@@ -2,5 +2,4 @@
 
 azure-devtools
 mock;python_version<="2.7"
-nose
-six
+nose
