Update copyright year of changed files

See https://github.com/spring-projects/spring-framework/issues/33823

Comment From: simonbasle

hey @ngocnhan-tran1996 thanks for the PR. we tend to decline polishing PRs, and the change was made on the 6.1.x branch so I'll go ahead and close this but I will directly fix the copyrights in the correct branch.

thanks for spotting the missing copyright year changes though 👍