Integrated: 8260857: Remove JNFWeakJObjectWrapper from Lanai Project

[Phil Race]

Needed to prevent future build breakage

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

Commit messages:
 - 8260857: Remove JNFWeakJObjectWrapper from Lanai Project

Changes: https://git.openjdk.java.net/lanai/pull/171/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=171&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260857
  Stats: 8 lines in 2 files changed: 2 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/lanai/pull/171.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/171/head:pull/171

PR: https://git.openjdk.java.net/lanai/pull/171