[2.18] Fix NPE in CatShardsRequestTests on version bump

[dbwiddis]

Description

One of the version changes from https://github.com/opensearch-project/OpenSearch/pull/16455/files was missed when it was manually backported in https://github.com/opensearch-project/OpenSearch/pull/16396.

The test in question is intended to check for a previous version that does not read the array of null strings. By leaving it at Version.CURRENT it bumped to 2.18.1 where 2.18.0 was the previous version and incorrectly tried to read that array.

Related Issues

Resolves #16580

Check List

• [x] Functionality includes testing.
• ~[ ] API changes companion pull request created, if applicable.~
• ~[ ] Public documentation issue/PR created, if applicable.~

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[github-actions[bot]]

:x: Gradle check result for 82d74adf0a128faff140f65810da07248cae0811: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions[bot]]

:white_check_mark: Gradle check result for 82d74adf0a128faff140f65810da07248cae0811: SUCCESS

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## 2.18 #16590 +/- ## ======================================= Coverage ? 71.82% Complexity ? 65367 ======================================= Files ? 5312 Lines ? 304995 Branches ? 44440 ======================================= Hits ? 219065 Misses ? 67681 Partials ? 18249 ```

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