Remove mock of not existing method in L3 agent UT.
Remove mock of not existing method in L3 agent UT.

There was mock of ri._get_floatingips_bound_to_host() in
L3 test_agent unit test module. This method was removed long time
ago in [1] so this mock is not necessary anymore.

TrivialFix

[1] https://review.opendev.org/#/c/499725/

Change-Id: Ia93cab667f8154663ba62b78bc0329ee16b8202c

mahak/neutron,openstack/neutron,mahak/neutron,openstack/neutron,mahak/neutron,openstack/neutron