RFR: 8292216: Remove modules/packages_unloading_do

[Coleen Phillimore]

These functions are no longer called. classes_unloading_do is called.
Built on linux-x64-debug.

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Commit messages:
 - 8292216: Remove modules/packages_unloading_do

Changes: https://git.openjdk.org/jdk/pull/9827/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9827&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292216
  Stats: 20 lines in 2 files changed: 0 ins; 18 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9827.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9827/head:pull/9827

PR: https://git.openjdk.org/jdk/pull/9827