Bump axios from 0.19.2 to 0.21.1 in /firebase/functions

Bumps [axios](https://github.com/axios/axios) from 0.19.2 to 0.21.1.
- [Release notes](https://github.com/axios/axios/releases)
- [Changelog](https://github.com/axios/axios/blob/v0.21.1/CHANGELOG.md)
- [Commits](axios/axios@v0.19.2...v0.21.1)

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Author: dependabot[bot]