client/Response: remove unused method Format()

src/client/Response.cxx

@@ -48,16 +48,6 @@ Response::FormatV(const char *fmt, std::va_list args) noexcept
 	return Write(FormatStringV(fmt, args).c_str());
 }
 
-bool
-Response::Format(const char *fmt, ...) noexcept
-{
-	std::va_list args;
-	va_start(args, fmt);
-	bool success = FormatV(fmt, args);
-	va_end(args);
-	return success;
-}
-
 bool
 Response::VFmt(fmt::string_view format_str, fmt::format_args args) noexcept
 {