CNDB-13027: Fix V5VectorPostingsWriter to handle omitted ordinals correctly

[jbellis]

What is the issue

https://github.com/riptano/cndb/issues/13027

[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

[jbellis]

Two issues:

1. The assert is just incorrect, I think this was a brain fart when I wrote it
2. "Create a Map of rowId -> ordinal" needs to skip OMITTED entries

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
80.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cassci-bot]

❌ Build ds-cassandra-pr-gate/PR-1584 rejected by Butler

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1 new test failure(s) in 2 builds
See build details here

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Found 1 new test failures

Test	Explanation	Branch history	Upstream history
o.a.c.u.b.BinLogTest.testTruncationReleasesLogS...	regression	🔴🔴	🔵🔵🔵🔵🔵🔵🔵

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Found 4 known test failures

[jkni]

LGTM. Thanks!