[lworld] RFR: 8376105: [lworld] Handle "lworld" branch GHA dry-runs

[Aleksey Shipilev]

Noticed that [JDK-8343546](https://bugs.openjdk.org/browse/JDK-8343546) filter does not work well with "lworld": a full test run is still running when on "lworld" sync in personal fork happens. We just need to filter "lworld" as well.

Additional testing:
 - [ ] GHA

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/valhalla/pull/1945/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1945&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376105
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1945.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1945/head:pull/1945

PR: https://git.openjdk.org/valhalla/pull/1945