RFR: 8326351: Update the Zlib version in open/src/java.base/share/legal/zlib.md to 1.3.1

[Lance Andersen]

Please review the updates to open/src/java.base/share/legal/zlib.md to update the file  from zlib 1.2.13 to zlib 1.3.1 which was missed as part of the PR for [JDK-8324632](https://bugs.openjdk.org/browse/JDK-8324632)

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Commit messages:
 - Update zlib.md for zlib 1.3.1

Changes: https://git.openjdk.org/jdk/pull/17935/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17935&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326351
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17935.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17935/head:pull/17935

PR: https://git.openjdk.org/jdk/pull/17935