Remove placement channel from statusbot

As placement repo is now under Nova governance, placement
channel is agreed to be merged to nova channel
- http://lists.openstack.org/pipermail/openstack-discuss/2020-November/019092.html

After this we should redirect placement channel to nova.

Change-Id: Ibd9fb49ac06ff70358aca62346c47e8a5c398bbe

hiera/common.yaml

@@ -57,7 +57,6 @@ statusbot_channels:
 - openstack-nova
 - openstack-oslo
 - openstack-outreachy
-- openstack-placement
 - openstack-qa
 - openstack-raksha
 - openstack-rally
@@ -146,7 +145,6 @@ meetbot_channels:
 - '#openstack-operators'
 - '#openstack-oslo'
 - '#openstack-outreachy'
-- '#openstack-placement'
 - '#openstack-qa'
 - '#openstack-rally'
 - '#openstack-release'