build: Bump clang minimum supported version to 17

src/util/overloaded.h

@@ -14,9 +14,6 @@ namespace util {
 //! Implementation comes from and example usage can be found at
 //! https://en.cppreference.com/w/cpp/utility/variant/visit#Example
 template<class... Ts> struct Overloaded : Ts... { using Ts::operator()...; };
-
-//! Explicit deduction guide (not needed after clang-17)
-template<class... Ts> Overloaded(Ts...) -> Overloaded<Ts...>;
 } // namespace util
 
 #endif // BITCOIN_UTIL_OVERLOADED_H