[vectorIntrinsics+compress] RFR: Compress JavaDoc.

[Paul Sandoz]

Add a little summary of compress/expand in the cross-lane section of the `Vector` class doc.

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Commit messages:
 - Compress JavaDoc.

Changes: https://git.openjdk.java.net/panama-vector/pull/162/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=162&range=00
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/162.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/162/head:pull/162

PR: https://git.openjdk.java.net/panama-vector/pull/162