[Issue 24571] Grammar spec should not use "opt"

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24571

Bolpat <qs.il.paperinik at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |qs.il.paperinik at gmail.com

--- Comment #1 from Bolpat <qs.il.paperinik at gmail.com> ---
Even a subscript or superscript question mark is better than `opt` as it
copy-pastes well.

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