RFR: 8318528: Rename TestUnstructuredLocking test

[Aleksey Shipilev]

Low-priority house-keeping. See the rationale in the bug.

Additional testing:
 - [x] macos-aarch64-server-fastdebug, affected test passes

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/16273/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16273&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318528
  Stats: 120 lines in 2 files changed: 60 ins; 60 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16273.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16273/head:pull/16273

PR: https://git.openjdk.org/jdk/pull/16273