Fix Xcode deprecation warning about sprintf usage

(cherry picked from commit b778c5caa3c030ab2a41798372cb54d6bfac4c16)

core/io/logger.cpp

@@ -151,10 +151,11 @@ void RotatedFileLogger::rotate_file() {
 
 	if (FileAccess::exists(base_path)) {
 		if (max_files > 1) {
-			char timestamp[21];
+			const size_t TIMESTAMP_SIZE = 21;
+			char timestamp[TIMESTAMP_SIZE];
 			OS::Date date = OS::get_singleton()->get_date();
 			OS::Time time = OS::get_singleton()->get_time();
-			sprintf(timestamp, "_%04d-%02d-%02d_%02d-%02d-%02d", date.year, date.month, date.day, time.hour, time.min, time.sec);
+			snprintf(timestamp, TIMESTAMP_SIZE, "_%04d-%02d-%02d_%02d-%02d-%02d", date.year, date.month, date.day, time.hour, time.min, time.sec);
 
 			String backup_name = base_path.get_basename() + timestamp;
 			if (base_path.get_extension() != String()) {