RFR: 8338489: Typo in MemorySegment doc

[Per Minborg]

This trivial PR proposes to fix a typo in the `MemorySegment` docs.

-------------

Commit messages:
 - Fix typo in MemorySegment docs

Changes: https://git.openjdk.org/jdk/pull/20727/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20727&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338489
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20727.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20727/head:pull/20727

PR: https://git.openjdk.org/jdk/pull/20727