RFR: JcstressRunner: remove artifact version duplication

[Evgeny Nikitin]

Tiny style-related fix: allows for modifying the artifact version in only one line.

Testing: some Jcstress tests using that Runner were run locally.

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Commit messages:
 - JcstressRunner: remove artifact version duplication

Changes: https://git.openjdk.java.net/loom/pull/117/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=117&range=00
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/loom/pull/117.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/117/head:pull/117

PR: https://git.openjdk.java.net/loom/pull/117