[vectorIntrinsics] RFR: Fix typo in VectorMask.laneIsSet

[Paul Sandoz]

Fix typo in VectorMask.laneIsSet.

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Commit messages:
 - Fix type in VectorMask.laneIsSet

Changes: https://git.openjdk.java.net/panama-vector/pull/142/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=142&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/142.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/142/head:pull/142

PR: https://git.openjdk.java.net/panama-vector/pull/142