[foreign-memaccess+abi] RFR: Fix broken link in JavaDoc

[Per Minborg]

This PR suggests fixing a broken link in the JavaDoc for the `ValueLayout` class.

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Commit messages:
 - Fix broken link in JavaDoc

Changes: https://git.openjdk.org/panama-foreign/pull/890/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=890&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/890.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign.git pull/890/head:pull/890

PR: https://git.openjdk.org/panama-foreign/pull/890