Remove BIND_DREAM_SERVICE permission from SystemUI.

This permission was added for the initial dream overlay
approach, but is not needed for the submitted implementation.

Test: atest CtsPermissionTestCases:android.permission.cts.ServicePermissionTest#testServicePermissions
Bug: 205419141
Change-Id: I347c7cb08d7c507a0896b680d637bf9f53e7a56a