Always enable draw_magnifier_border_outside_wmlock

It was enabled several weeks without problem.
Because it is for fixing deadlock bug, remove the flag directly.

Bug: 318327737
Bug: 276845499
Test: atest WindowManagerServiceTests#testDrawMagnifiedViewport
Test: atest AccessibilityMagnificationTest
Change-Id: I2523711d8cc02f2d940882aac7d6793d183c8ea3