RFR: 8332251: javadoc: incorrect reference in Region.getPrefWidth/Height

[Andy Goryachev]

The javadoc for `Region.getPrefHeight() / getPrefWidth()` incorrectly refers to `getPrefHeight(forWidth) / getPrefWidth(forHeight)`

should be

`prefHeight(forWidth) / prefWidth(forHeight)`

- also converted these references to `{@link}`s.

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Commit messages:
 - 8332251: javadoc: incorrect reference in Region.getPrefWidth/Height

Changes: https://git.openjdk.org/jfx/pull/1456/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1456&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332251
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1456.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1456/head:pull/1456

PR: https://git.openjdk.org/jfx/pull/1456