Update License

Someone opened a PR to do this a few days ago. I posted a comment. When I was ready to return to the ticket, I couldn't find it as opened or closed. It seemed like a reasonable idea. I will submit this PR for now and sit on it for about a week to give the original author a chance to resubmit.

Author: oleibman

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2019 PhpSpreadsheet Authors
+Copyright (c) 2019-2025 PhpSpreadsheet Authors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal