Deprecate retailDemo permission protection flag.

Because it has been replaced by the retail demo role in V and is only
used by PACKAGE_USAGE_STATS right now.

We can't simply remove it because it's a system API.

Bug: 294122862
Test: presubmit
Change-Id: I3ca7a956ceb859578b0b07de598c3a06c5c693d7
3 files changed