Turn off voice access in 16KB mode

VoiceAccess doesn't support the 16KB mode yet. Skipping
voice accesss service when in page-agnostic mode.

Test: m Settings && adb install -r $ANDROID_PRODUCT_OUT/system_ext/priv-app/Settings/Settings.apk
Bug: 335443194
Bug: 340231742
Change-Id: If4deae48aaa221c843af5eb65208659ad38a08b2