RFR: 8283203: Fix typo in SystemTray.getTrayIconSize javadoc

[SWinxy]

Please review this itty-bitty typo fix.

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Commit messages:
 - 8283203: Fix typo in SystemTray.getTrayIconSize javadoc

Changes: https://git.openjdk.org/jdk/pull/12020/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12020&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8283203
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12020.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12020/head:pull/12020

PR: https://git.openjdk.org/jdk/pull/12020