updated dialog title to include title + description for A11y

Test: manual - using talkback ensure that when a customization dialog
pops in the title and the description is announced.
Flag: com.android.systemui.keyboard_shortcut_helper_shortcut_customizer
Fix: 390316097
Fix: 390311388

Change-Id: I6530886e3848a3603791619e61c6fc4d6af7f5fe