[lworld] RFR: 8329234: [lworld] compiler/gcbarriers/TestZGCBarrierElision.java fails after JDK-8329205

[Damon Fenacci]

The `compiler/gcbarriers/TestZGCBarrierElision.java` test failed after [JDK-8329205](https://bugs.openjdk.org/browse/JDK-8329205) but [JDK-8350515](https://bugs.openjdk.org/browse/JDK-8350515) fixed the issue.
This PR removes the TODO and uncomments the IR check.

Tests: Tier 1-3+

-------------

Commit messages:
 - JDK-8329234: [lworld] compiler/gcbarriers/TestZGCBarrierElision.java fails after JDK-8329205

Changes: https://git.openjdk.org/valhalla/pull/1496/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1496&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329234
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/1496.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1496/head:pull/1496

PR: https://git.openjdk.org/valhalla/pull/1496