PES-3306 Reduced chunk size for handling janusgraph<>cassandra statement batch issue

[hr2904]

Change description

When running cleanup on Nelnet, getting
Caused by: java.lang.IllegalStateException: Batch statement cannot contain more than 65535 statements. This is a quick unblock we are providing to the customer by reducing chunk size.

Type of change

• Bug fix (fixes an issue)

Related issues

Fix #1

Checklists

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• "Ready for review" label attached and reviewers assigned
• Changes have been reviewed by at least one other contributor
• Pull request linked to task tracker where applicable