[foreign-memaccess+abi] RFR: Fix override in ValueLayout

[Per Minborg]

This PR fixes an override of `withoutName()` that is missed.

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Commit messages:
 - Fix override in ValueLayout

Changes: https://git.openjdk.org/panama-foreign/pull/816/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=816&range=00
  Stats: 16 lines in 2 files changed: 16 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/816.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/816/head:pull/816

PR: https://git.openjdk.org/panama-foreign/pull/816