Update variables.md

[amanKumarcodx]

I update the data type and add return 0 that the function does not any value. thank you.

Description

Issue Solved

Type of Change

• Adding a new entry
• Editing an existing entry (fixing a typo, bug, issues, etc)
• Updating the documentation

Checklist

• [x ] All writings are my own.
• [ x] My entry follows the Codecademy Docs style guide.
• [ x] My changes generate no new warnings.
• [ x] I have performed a self-review of my own writing and code.
• [ x] I have checked my entry and corrected any misspellings.
• [ x] I have made corresponding changes to the documentation if needed.
• [ x] I have confirmed my changes are not being pushed from my forked main branch.
• [ x] I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• [ x] I have linked any issues that are relevant to this PR in the Issues Solved section.

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[SaviDahegaonkar]

Hey @amanKumarcodx , I tried reviewing this PR but I found that this PR does not mentions the issue it closes or refers to, due to which I feel this PR is invalid. So I will have to close this and you can create a new PR tracing the issue which that particular PR closes and also follows the documentation stye-guide.