Integrated: remove hidden option allowNullRestrictedTypesForValueClassesOnly

[Vicente Romero]

just removing a hidden option that is not meaningful anymore

-------------

Commit messages:
 - remove hidden option allowNullRestrictedTypesForValueClassesOnly

Changes: https://git.openjdk.org/valhalla/pull/1851/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1851&range=00
  Stats: 56 lines in 3 files changed: 0 ins; 56 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1851.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1851/head:pull/1851

PR: https://git.openjdk.org/valhalla/pull/1851