Remove dependecy testrepository
testr is part of testrepository, we invoke testr through os-testr
in Cinder and  testrepository is dpendency of os-testr, we don't
invoke testr directly, so don't need dependency testrepository.
@@ -16,7 +16,6 @@ PyMySQL>=0.7.6 # MIT License
psycopg2>=2.5 # LGPL/ZPL
python-subunit>=0.0.18 # Apache-2.0/BSD
testtools>=1.4.0 # MIT
-testrepository>=0.0.18 # Apache-2.0/BSD
testresources>=0.2.4 # Apache-2.0/BSD
testscenarios>=0.4 # Apache-2.0/BSD
oslosphinx>=4.7.0 # Apache-2.0
