RFR: 8316967: Remove unnecessary vmtimer from UnregisteredClasses::load_class

[Calvin Cheung]

Simple fix for removing the vmtimer from `UnregisteredClasses::load_class` and the corresponding `PerfClassTraceTime` constructor.

Passed tier1 testing.

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Commit messages:
 - 8316967: Remove unnecessary vmtimer from UnregisteredClasses::load_class

Changes: https://git.openjdk.org/jdk/pull/16046/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16046&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316967
  Stats: 13 lines in 2 files changed: 0 ins; 13 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16046.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16046/head:pull/16046

PR: https://git.openjdk.org/jdk/pull/16046