Do not dismiss split while exit PiP to full-screen

The dismiss-split-on-exit-pip code path was added back in ag/23447537.
Deprecate this path since no regressions' found.

Flag: EXEMPT bugfix
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/encWvtoZUnUWtxd9MIlltz
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/gE1jnO3OMTJw04Axi08Ou5
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/hlqwTIhGKiJcr0e4oTeL0M
Bug: 358041194
Test: Enter PiP from split-screen from multiple apps
Test: Create split-screen from apps in PiP mode
Change-Id: Ie98bd68d0b52f8280c36c28f78b5216f93eef710