fup: fix docsting in manager.py

As discussed in Ie274f199ce33199a6fc8c4d6846a853522a90d3a there is an
unnecessary colon in create_networks docstring.

Change-Id: I4f6af233f8b45d2533cf3d224f1d719e28778941
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index f053dc1..da41d62 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -1268,7 +1268,7 @@
         :param tenant_id: id of tenant to create resources in.
         :param dns_nameservers: list of dns servers to send to subnet.
         :param port_security_enabled: whether or not port_security is enabled
-        :param: net_dict: a dict containing experimental network information in
+        :param net_dict: a dict containing experimental network information in
                 a form like this: {'provider:network_type': 'vlan',
                                    'provider:physical_network': 'foo',
                                    'provider:segmentation_id': '42'}