RFR: 8338447: Remove InstanceKlass::_is_marked_dependent

[Coleen Phillimore]

Please review this trivial change.  I ran the SA tests to make sure the is_marked_dependent flag in vmStructs wasn't used there.

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

Commit messages:
 - 8338447: Remove InstanceKlass::_is_marked_dependent

Changes: https://git.openjdk.org/jdk/pull/20595/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20595&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338447
  Stats: 5 lines in 2 files changed: 0 ins; 5 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20595.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20595/head:pull/20595

PR: https://git.openjdk.org/jdk/pull/20595