Change MANAGE_ROLLBACKS permission to signature|verifier

It was set to signature|installer so that Phonesky would have access to
the RollbackManager APIs, but Phonesky is the verifier, not the
installer.

Test: atest RollbackTest
Test: atest CtsPermission2TestCases:PermissionPolicyTest
Bug: 112431924
Change-Id: I45fbe3fe2e618517bca1fd93f35324f93851868c