Fix Biometric Prompt icon acting as button for a11y

Biometric Prompt icon should only act as a button for a11y when coex is
enabled and auth confirmation is needed.

Fixes: 373535676
Fixes: 373791333
Fixes: 374003773
Flag: EXEMPT bugfix
Test: atest SystemUITests:com.android.systemui.biometrics
Change-Id: I25290c0239ca97354d5f91e084ed78c091d0ae1e