Fix a typo in test_security_groups.py

This patch removes the superfluous 'that'.

TrivialFix

Change-Id: I2515eb26dbdff0f0f3a2f465d1c1feb08599ef5c
diff --git a/tempest/api/network/test_security_groups.py b/tempest/api/network/test_security_groups.py
index 5312979..1031ab8 100644
--- a/tempest/api/network/test_security_groups.py
+++ b/tempest/api/network/test_security_groups.py
@@ -71,7 +71,7 @@
     @test.attr(type='smoke')
     @test.idempotent_id('e30abd17-fef9-4739-8617-dc26da88e686')
     def test_list_security_groups(self):
-        # Verify the that security group belonging to project exist in list
+        # Verify the security group belonging to project exist in list
         body = self.security_groups_client.list_security_groups()
         security_groups = body['security_groups']
         found = None