[clang-tools-extra] [clang-tidy][NFC] Don't store a redundant copy of `HeaderFileExtensions` in every check (PR #190302)

[Victor Chernyakin via cfe-commits]

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@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "GlobalNamesInHeadersCheck.h"
+#include "../utils/FileExtensionsUtils.h"
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localspook wrote:

This is needed to bring in functions like `utils::getFileExtension`

https://github.com/llvm/llvm-project/pull/190302