CC5 fix AlterTest

[djatnieks]

What is the issue

Fixes https://github.com/riptano/cndb/issues/14954

What does this PR fix and why was it fixed

Fixes CC5 test failure by removing an assert that was likely due to a rebase mistake.

        assertThat(AbstractShardedMemtable.getDefaultShardCount()).isEqualTo(1);;

The assert comes from a CC ticket, STAR-840, but this assert does not appear on main branch in AlterTest. In fact AbstractShardedMemtable is a CC 5.0 only class.
Without digging more into the history of how/why this got added ... it's not needed here since the main branch version does not have any similar check.

[github-actions]

Checklist before you submit for review

• Make sure there is a PR in the CNDB project updating the Converged Cassandra version
• Use NoSpamLogger for log lines that may appear frequently in the logs
• Verify test results on Butler
• Test coverage for new/modified code is > 80%
• Proper code formatting
• Proper title for each commit staring with the project-issue number, like CNDB-1234
• Each commit has a meaningful description
• Each commit is not very long and contains related changes
• Renames, moves and reformatting are in distinct commits
• All new files should contain the DataStax copyright header instead of the Apache License one

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cassci-bot]

✔️ Build ds-cassandra-pr-gate/PR-1921 approved by Butler

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Approved by Butler
See build details here