Remove ECM check from isAccessibilityTargetAllowed

This check is redundant, as we already check ECM at enable time, and it
is causing issues with the new in-call ECM restricted state

Fixes: 389147067
Test: atest AccessibilityManagerServiceTest, AccessibilityManagerTest
Flag: EXEMPT beta 2 cherry pick
Change-Id: I3945d94138200a7d0be4af7a1cdd7f6b7da600e0