RFR: 8305242: Remove non-invariant assert(EventThreadDump::is_enabled())

[Markus Grönlund]

Greetings,

removing a non-invariant assert for EventThreadDump::is_enabled()).

Thanks
Markus

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Commit messages:
 - 8305242

Changes: https://git.openjdk.org/jdk/pull/13243/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13243&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305242
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13243.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13243/head:pull/13243

PR: https://git.openjdk.org/jdk/pull/13243