docs: fix copyright year to 2026 on new elastic training guide

Author: inardini

docs/run_maxtext/run_maxtext_elastic_training.md

@@ -1,5 +1,5 @@
 <!--
- Copyright 2025 Google LLC
+ Copyright 2026 Google LLC
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.