RFR: 8369820: FX: Update copyright year in docs, readme files to 2026

[Ambarish Rapte]

Update Copyright year in the 3 doc files to 2026.

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Commit messages:
 - doc copyright year update

Changes: https://git.openjdk.org/jfx/pull/1939/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1939&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8369820
  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1939.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1939/head:pull/1939

PR: https://git.openjdk.org/jfx/pull/1939