[clang-tools-extra] [clang-tidy] Update llvmlibc-implementation-in-namespace to new rules (PR #66504)

[Piotr Zegar via cfe-commits]

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@@ -30,15 +32,18 @@ void ImplementationInNamespaceCheck::check(
     return;
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PiotrZSL wrote:

this could be replaced with `decl(isExpansionInMainFile())`

https://github.com/llvm/llvm-project/pull/66504