Removed force_flush arg from everywhere. Use flush_on(level) instead

tests/errors.cpp

@@ -28,6 +28,7 @@ TEST_CASE("custom_error_handler", "[errors]]")
     prepare_logdir();
     std::string filename = "logs/simple_log.txt";
     auto logger = spdlog::create<spdlog::sinks::simple_file_sink_mt>("logger", filename, true);
+	logger->flush_on(spdlog::level::info);
     logger->set_error_handler([=](const std::string& msg)
     {
         throw custom_ex();