[nostalgia/core] Rename event handler to update handler

src/nostalgia/core/glfw/core.hpp

@@ -11,7 +11,7 @@ namespace nostalgia::core {
 struct GlfwImplData {
 	struct GLFWwindow *window = nullptr;
 	int64_t startTime = 0;
-	event_handler eventHandler = nullptr;
+	UpdateHandler eventHandler = nullptr;
 	uint64_t wakeupTime = 0;
 };