RFR: 8279078: Update copyright header for files modified in 2021

[Ambarish Rapte]

Fix for updating last modified year in the files that were modified during year 2021.
@kevinrushforth, Please take a look.

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Commit messages:
 - copyright year update 2021

Changes: https://git.openjdk.java.net/jfx/pull/699/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=699&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279078
  Stats: 75 lines in 74 files changed: 0 ins; 0 del; 75 mod
  Patch: https://git.openjdk.java.net/jfx/pull/699.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/699/head:pull/699

PR: https://git.openjdk.java.net/jfx/pull/699