[foreign-memaccess+abi] RFR: Fix bad call to segment factory in VarHandleExactTest

[Maurizio Cimadamore]

Running more tests I found another place which was not rewritten to use the new static factory names.

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Commit messages:
 - Fix bad call to segment factory in VarHandleExactTest

Changes: https://git.openjdk.java.net/panama-foreign/pull/506/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=506&range=00
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/506.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/506/head:pull/506

PR: https://git.openjdk.java.net/panama-foreign/pull/506