Update airplane mode key to match framework constant

Change pref key for airplane mode to "airplane_mode" to match the
constant declared in SettingsSlicesContract.

Bug: 80106671
Test: robotests
Change-Id: I625bed440dd7f1f8509cd00ced5ba67f08a0e737
Merged-In: I898befffbdafc3004fc127414edd04f60ff2554e
5 files changed