RFR: 8331214: Doc: update spec for SpinnerFactory classes

[drmarmac]

This PR updates the javadoc for the SpinnerFactory wrap-around behavior introduced in #1431.

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Commit messages:
 - Update SpinnerValueFactory documentation

Changes: https://git.openjdk.org/jfx/pull/1450/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1450&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331214
  Stats: 21 lines in 1 file changed: 13 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jfx/pull/1450.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1450/head:pull/1450

PR: https://git.openjdk.org/jfx/pull/1450