[clang] [clang] Fix false positive with -Wdocumentation and explicit instanti… (PR #178223)

[Mariya Podchishchaeva via cfe-commits]

Fznamznon wrote:

I'm not familiar enough with `-Wdocumentation` so let's probably wait for Aaron. C standard meetings are happening this week, so his replies are delayed.

https://github.com/llvm/llvm-project/pull/178223