RFR: 8336592: Wrong type in documentation for TreeTableView

[ANUPAM DEV]

Hello,

There was a typo in the documentation of TreeTableView.
I have changed TreeTableColumns to TreeTableColumn

Please review.

Regards,
Anupam

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Commit messages:
 - Update TreeTableView.java

Changes: https://git.openjdk.org/jfx/pull/1510/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1510&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336592
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/1510.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1510/head:pull/1510

PR: https://git.openjdk.org/jfx/pull/1510