Remove transitional support for influxdb in cloudkitty upgrade

During the Stein release the default storage backend for cloudkitty was
switched to influxdb. To aid this transition we added creation of the
influxdb database during upgrade. Now that this transition is complete
we can remove it.

Change-Id: Ieb247f36af932d3a357504c7419ead44b10d1301

ansible/roles/cloudkitty/tasks/upgrade.yml

 ---
 - include_tasks: config.yml
 
-# NOTE(mgoddard): Transition support for upgrades from Rocky or Stein which may
-# be using the SQLAlchemy storage backend.
-# TODO(mgoddard): Remove in U cycle.
-- name: Creating Cloudkitty influxdb database
-  become: true
-  kolla_toolbox:
-    module_name: influxdb_database
-    module_args:
-      hostname: "{{ influxdb_address }}"
-      port: "{{ influxdb_http_port }}"
-      database_name: "{{ cloudkitty_influxdb_name }}"
-  when: cloudkitty_storage_backend == 'influxdb'
-
 - include_tasks: bootstrap_service.yml
 
 - name: Flush handlers