Remove VibrationAttributes#CATEGORY_KEYBOARD (in framework)

Since CL[1], [2] introduced USAGE_IME_FEEDBACK in VibrationAttributes
to be able to specify default / current vibration in VibrationSettings
according to the vibration usage naturally without using this category
attribute + a bypass flag to only support a fixed vibration scaling.

Remove CATEGORY_KEYBOARD and usage in framework for cleaning up logic.

[1]: I6256c4f47a8bbee4b649d35eabfbc0c94215c0d7
[2]: I764aa8bd72889d4af62b30bff75af9033f22052b

Flag: EXEMPT refactor
Bug: 332661766
Test: atest VibrationSettingsTest, VibrationScalerTest
Test: atest HapticFeedbackVibrationProviderTest
Change-Id: I4780814138adfd67eb94363967325515420736d8