RFR: 7903969: Update year in copyright message

[Christian Stein]

Please review this change updating the second year of the copyright to 2025.

This PR also removes the copyright from command-line printouts of `jtreg` and `jtdiff`, for example in `jtreg --help` calls.

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Commit messages:
 - 7903969: Update year in copyright message

Changes: https://git.openjdk.org/jtreg/pull/254/files
  Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=254&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903969
  Stats: 11 lines in 4 files changed: 0 ins; 6 del; 5 mod
  Patch: https://git.openjdk.org/jtreg/pull/254.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/254/head:pull/254

PR: https://git.openjdk.org/jtreg/pull/254