Remove ACL for refs/heads/release- for mistral
Remove ACL for refs/heads/release- for mistral

This ACL section is unused with current workflow and there
are no remote branches with this name for mistral.

Change-Id: I3a3436a4ef65242cb05c7f8d85720128e4cc9514

Tesora/tesora-project-config,dongwenjuan/project-config,noorul/os-project-config,openstack-infra/project-config,dongwenjuan/project-config,noorul/os-project-config,openstack-infra/project-config,Tesora/tesora-project-config