Update NOTICE year 2025 -> 2026 (#3332)

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Author: kevinjqliu

NOTICE

@@ -1,6 +1,6 @@
 
 Apache Iceberg
-Copyright 2017-2025 The Apache Software Foundation
+Copyright 2017-2026 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).