Remove get_networks

As tempest.scenario.manager was announced stable interface in Tempest 27.0.0[1] it can be now reused in plugins.

Replaced methods:
	* get_networks (not used)

Etherpad concerning this effort:
https://etherpad.opendev.org/p/tempest-scenario-manager-cleanup

[1] https://docs.openstack.org/releasenotes/tempest/v27.0.0.html#release-notes-27-0-0

Change-Id: Ibb40445426fcf350ca6999558252f288a65a7dbf
diff --git a/manila_tempest_tests/tests/scenario/manager.py b/manila_tempest_tests/tests/scenario/manager.py
index cb496a0..d533e22 100644
--- a/manila_tempest_tests/tests/scenario/manager.py
+++ b/manila_tempest_tests/tests/scenario/manager.py
@@ -160,9 +160,6 @@
                             "Unable to get network by name: %s" % identifier)
         return networks[0]
 
-    def get_networks(self):
-        return self.os_admin.networks_client.list_networks()['networks']
-
     def create_floating_ip(self, thing, external_network_id=None,
                            port_id=None, ip_addr=None, client=None):
         """Create a floating IP and associates to a resource/port on Neutron"""