fixing signed/unsigned in test attributes

Author: felixjulianheitmann

tests/test_attributes.cpp

@@ -173,7 +173,7 @@ TEST_CASE("attribute test - nested scoped") {
 }
 
 TEST_CASE("attribute test - multi threaded") {
-    const int n_tasks = std::thread::hardware_concurrency();
+    const auto n_tasks = std::thread::hardware_concurrency();
     constexpr auto n_values = 30;
     auto mt_sink = std::make_shared<spdlog::sinks::test_sink_mt>();
     auto logger = spdlog::logger("logger", mt_sink);