Remove Vinita from codeowners

[BenHenning]

Explanation

Since Vinita is taking a step back from Oppia work, removing her from the codeowners list so that she doesn't have any code reviewer expectations.

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".) (N/A)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

For UI-specific PRs only

N/A -- This is a codeowner-only change.

[BenHenning]

@seanlip PTAL for codeowner change approval.

[seanlip]

Thanks, LGTM!