Include isMainUser() calls on dumpsys user.

That method is deprecated but still widely used, so it will be useful
to track its usage.

Bug: 414326600
Bug: 390264303
Test: adb shell dumpsys user --deprecated-calls
Test: adb shell dumpsys user | grep "called isMainUser"
Flag: EXEMPT debugging changes

Change-Id: I15625b5671b3ef23f3de621fd98aaa8562f84108