RFR: 8310874: Runthese30m crashes with klass should be in the placeholders during verification

[Coleen Phillimore]

For non-parallel capable class loaders, the class is not put in the placeholders table, so a verification at the wrong time will hit this assert.  This trivial change removes the invalid assert.
Tested with inserting a LoaderConstraintTable::verify while running jck tests.

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Commit messages:
 - 8310874: Runthese30m crashes with guarantee(entry != nullptr) failed: klass should be in the placeholders during verification

Changes: https://git.openjdk.org/jdk/pull/14887/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14887&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310874
  Stats: 9 lines in 1 file changed: 0 ins; 9 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14887.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14887/head:pull/14887

PR: https://git.openjdk.org/jdk/pull/14887