Remove StatusBar#getStatusBarView

StatusBar shouldn't be handing out references to StatusBarView, since
PhoneStatusBarView doesn't have the same lifetime as StatusBar.java. All
calls to this method have been removed so we can just delete it now.

Bug: 209005990
Test: atest SytemUITests
Change-Id: Ib277941d739290445668589932fb65b1b94fb154