[Issue 21458] missed oportunity to progapage final to its its aliased symbol

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21458

--- Comment #2 from Basile-z <b2.temp at gmx.com> ---
note that

---
class Y {}
class A(T) {}
alias B = final A!Y;
class C : B {}
---

gives

> /tmp/temp_7F8354048F90.d:7:20: Deprecation: storage class `final` has no effect in type aliases

which is a bit better

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