Merge "Add FLAG_IMMUTABLE to PendingIntent in LegacyModeSmsHandler." into pi-dev am: 44b02956c4 am: 06572a0820 am: 5625595e77 am: 0642423c12 am: 30d5474b58 am: e178da4943 am: 80706f5bd6

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

Change-Id: Ib905eb1d7be1c2cdc3f1f97dab5e3a786b9e1de7