Merge "Add FLAG_IMMUTABLE to PendingIntent in LegacyModeSmsHandler." into pi-dev am: 44b02956c4 am: 06572a0820 am: 5625595e77

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Dialer/+/16199731

Change-Id: I37a97bebc3035269ae9b4a3ded2a23f828daec53