[libc++][NFC] Remove unused struct in <string> (#106527)

Author: philnik777

libcxx/include/string

@@ -3462,14 +3462,6 @@ inline _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocat
 
 // find
 
-template <class _Traits>
-struct _LIBCPP_HIDDEN __traits_eq {
-  typedef typename _Traits::char_type char_type;
-  _LIBCPP_HIDE_FROM_ABI bool operator()(const char_type& __x, const char_type& __y) _NOEXCEPT {
-    return _Traits::eq(__x, __y);
-  }
-};
-
 template <class _CharT, class _Traits, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT {