RFR: 8378880: GenShen: Fix typo in recent conversion to atomic field

[William Kemper]

Fix typo

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Commit messages:
 - Fix typo

Changes: https://git.openjdk.org/jdk/pull/29972/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29972&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378880
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29972.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29972/head:pull/29972

PR: https://git.openjdk.org/jdk/pull/29972