No longer checking realCallingUid in #getLaunchRootTask

The changes was originally added for Bubbles in commit f65e02d5
and this should not be needed anymore since Bubbles are no longer
implemented via virtual displays.

In addition, we probably shouldn't elevate the privileges when
the PendingIntent is launched from another uid.

Bug: 184806710
Test: wm presubmit
Change-Id: If90841372ee419bfe2e4ce7480e1e763b7a6df1a