[a11y] fix the issue where launcher announces item added to homescreen before

it does

Test:
1. long press on home screen -> widgets
2. enable talkback
3. add a custom shortcut to home screen (i.e. 1x1 widgets, e.g. drive
scan in Google Drive, Driving Mode in Google Maps ... e.t.c )
4. verify talkback announces "item addded to homescreen" after it does
get added to the homescreen
5. repeat the same test for widgets (e.g. calendar)

Bug: 141527338
Change-Id: I232e6e796c9edb81128f816c71a33310c3700e73