[Issue 23361] std.uni.normalize should be pure

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23361

--- Comment #2 from Imperatorn <johan_forsberg_86 at hotmail.com> ---
One way I guess is to cast the function to pure.
The other is to actually mark _d_arrayshrinkfit as pure.

Which of those seems most reasonable?

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