fix: correct expected value in variance doc-test

[AnshuKanrar]

1. This PR fixes or fixes part of [BUG]: Incorrect expected value in variance.rs doc-test #15 .
2. This PR does the following: Fix Bug in doc-test

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• The PR title starts with "Fix [BUG]: Incorrect expected value in variance.rs doc-test #15 : ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
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Proof that changes are correct