Observable and reactive variables can not be final

[akhdari]

Problem:
in getx/documentation/en_US
/state_management.md
Starting from this part of the documentation https://github.com/jonataslaw/getx/blob/master/documentation/en_US/state_management.md#declaring-a-reactive-variable,
in the examples provided, observable and reactive variables are declared with their access modifiers set to final.

Solution:
Replace final with var.

Reason for the modification:
Reactive and observable variables are mutable and cannot be set to final.

[brasizza]

Actually the properties is not mutable, the reactivity is.

final name = "marcus".obs;
Name is final and cannot been changed, but name.value = "MARCUS"; can.