fix: upgrade mongoose from 6.11.4 to 6.12.7

Snyk has created this PR to upgrade mongoose from 6.11.4 to 6.12.7.

See this package in npm:
https://www.npmjs.com/package/mongoose

See this project in Snyk:
https://app.snyk.io/org/amay0808/project/2b617d8d-948e-4262-a519-8e3809cdb06f?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot