CNDB-18059 increase expected disk size to fit on CI

[k-rus]

What is the issue

Fixes https://github.com/riptano/cndb/issues/18059

During running the SaiDiskSizeTest on CI the actual used disk size was slightly bigger than expected, while no changes were done during the format.

What does this PR fix and why was it fixed

Increases expecting value for the case to fix the test failure and fit the actual size into the expected range.

[github-actions]

Checklist before you submit for review

• This PR adheres to the Definition of Done
• Make sure there is a PR and ticket 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 IBM copyright header instead of the Apache License one (no DataStax copyright any longer)

[k-rus]

• Make sure there is a PR and ticket in the CNDB project updating the Converged Cassandra version

Only test is changed, thus no CNDB's PR.

[plpesvc-ds]

❌ Build ds-cassandra-pr-gate/PR-2446 rejected by Butler

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4 regressions found
See build details here

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Found 4 new test failures

Test	Explanation	Runs	Upstream
o.a.c.db.compaction.unified.ShardedMultiWriterTest.testShardedCompactionWriter_fiveShards[isReplicaAware=true] (compression)	REGRESSION	🔴	0 / 30
o.a.c.index.sai.QueryContextTest.testWideTableScoreOrdered[ec] (compression)	REGRESSION	🔴	0 / 30
o.a.c.index.sai.cql.VectorCompaction100dTest.testOneToManyCompaction[version=ec enableNVQ=true]	REGRESSION	🔴	0 / 30
o.a.c.index.sai.cql.VectorSiftSmallTest.testSiftSmall[ed false]	REGRESSION	🔴	0 / 30

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Found 3 known test failures

[ekaterinadimitrova2]

I am against merging this PR. It doesn't fix the underlying issue. I explained on the GH issue why.