Revert "ec2api: Use volumev3 instead of volumev2"

This reverts commit 01f74c0ba5.

Reason for revert:
Now ec2api uses volumev3 by default so we don't need to set
it explicitly.

Depends-on: https://review.opendev.org/768182

Change-Id: I486c6f66294529544f0f2469ce2436bad935e957

manifests/ec2api.pp

@@ -31,7 +31,6 @@ class openstack_integration::ec2api {
       }
       class { 'ec2api::api':
         keystone_ec2_tokens_url => "${::openstack_integration::config::keystone_auth_uri}/v3/ec2tokens",
-        cinder_service_type     => 'volumev3',
         external_network        => 'public',
       }
       include ec2api::metadata