[Contextual Edu] Accessibility - Adjust font style for dialog

The text should not be bold in default mode according to spec.

The text will be bold automatically when bold option is enabled in accessibility.

Test result
bold disabled (Default mode): https://screenshot.googleplex.com/6kfrkmCdfYMpzda
bold enabled: https://screenshot.googleplex.com/3sgvScdqnSy8VEx

Bug: 374661231
Test: add screenshot test in b/370908143
Flag: com.android.systemui.keyboard_touchpad_contextual_education

Change-Id: I5f935434fee7300208c6a1446edde254c89d78e2