ICU-22589 Avoid timeout in TimeZone test

[FrankYFTang]

The bug was filed because the fuzzer test data is very large and take a long time to run. Not an infinity loop. This PR limit the data to at most 2000 bytes so it will complete in reasonable amount of time.

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22589
• Required: The PR title must be prefixed with a JIRA Issue number.
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• Required: Each commit message must be prefixed with a JIRA Issue number.
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[richgillam]

LGTM.