[jdk21u-dev] RFR: 8316002: Remove unnecessary seen_dead_loader in ClassLoaderDataGraph::do_unloading

[Goetz Lindenmaier]

I backport this for parity with 21.0.4-oracle.

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Commit messages:
 - Backport 50158f393e0b077b22886f44624ff23e65dedeb8

Changes: https://git.openjdk.org/jdk21u-dev/pull/426/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=426&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316002
  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/426.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/426/head:pull/426

PR: https://git.openjdk.org/jdk21u-dev/pull/426