Revert "Allow activity in ActivityEmbedding split to get Task windowing mode"

This reverts commit 0522842a349dec60892784c34c1b337490ee39d7.

Reason for revert: Breaking PlatformScenarioTests Tests due to NPE

Bug: 230793322
Change-Id: Ib6a9a1b7fb1c95681fc7a1bb959da5618b840f16
6 files changed