[jfx19] RFR: 8286678: Fix mistakes in FX API docs

[Nir Lisker]

Fixes the mistakes in the JBS ticket and some additional minor corrections.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jfx/pull/880/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=880&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286678
  Stats: 30 lines in 7 files changed: 1 ins; 2 del; 27 mod
  Patch: https://git.openjdk.org/jfx/pull/880.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/880/head:pull/880

PR: https://git.openjdk.org/jfx/pull/880