[clang] Revert "Reland "[Clang] Enable -Wunused-template under -Wall" (#208001)" (PR #218638)

[Mariya Podchishchaeva via cfe-commits]

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@@ -238,11 +225,6 @@ features cannot lower the translation-unit ABI level;
 
 - More consistent rendering of Unicode characters in diagnostic messages.
 
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Fznamznon wrote:

I'm confused, the patch went to 23, but the release note is still in main? Did we not clear release notes yet?

https://github.com/llvm/llvm-project/pull/218638