Bump the copyright year.

A big thank you to the Founding Fathers of Serfdom for putting
the year into just this one file.

* NOTCE: Change 2025 to 2026.


git-svn-id: https://svn.apache.org/repos/asf/serf/trunk@1931320 13f79535-47bb-0310-9956-ffa450edef68

Author: brainy

NOTICE

@@ -1,5 +1,5 @@
 Apache Serf
-Copyright 2025 The Apache Software Foundation
+Copyright 2026 The Apache Software Foundation
 
 This product includes software developed by many people, and distributed
 under Contributor License Agreements to The Apache Software Foundation