Update footer string for hearing device related pages

Users sometimes will confuse why their device is not shown on hearing device related pages. Describe more that only ASHA and LE Audio hearing aids will be listed in
these pages to let them know the reason.

Bug: 326167961
Test: build pass, only simple string update
Change-Id: I624c7a23e98c04f0a659742f63465918a45bb888