build(deps): bump engine.io, gatsby, gatsby-plugin-react-helmet and gatsby-plugin-sass

Bumps [engine.io](https://github.com/socketio/engine.io) to 6.2.1 and updates ancestor dependencies [engine.io](https://github.com/socketio/engine.io), [gatsby](https://github.com/gatsbyjs/gatsby), [gatsby-plugin-react-helmet](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-react-helmet) and [gatsby-plugin-sass](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-sass). These dependencies need to be updated together.


Updates `engine.io` from 4.1.2 to 6.2.1
- [Release notes](https://github.com/socketio/engine.io/releases)
- [Changelog](https://github.com/socketio/engine.io/blob/main/CHANGELOG.md)
- [Commits](socketio/engine.io@4.1.2...6.2.1)

Updates `gatsby` from 3.14.6 to 5.7.0
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/compare/[email protected]@5.7.0)

Updates `gatsby-plugin-react-helmet` from 4.14.0 to 6.7.0
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-react-helmet/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-plugin-react-helmet)

Updates `gatsby-plugin-sass` from 4.14.0 to 6.7.0
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-sass/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-plugin-sass)

---
updated-dependencies:
- dependency-name: engine.io
  dependency-type: indirect
- dependency-name: gatsby
  dependency-type: direct:production
- dependency-name: gatsby-plugin-react-helmet
  dependency-type: direct:production
- dependency-name: gatsby-plugin-sass
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]