build(deps): bump gatsby-remark-copy-linked-files in /docs

Bumps [gatsby-remark-copy-linked-files](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-copy-linked-files) from 2.3.12 to 2.7.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-remark-copy-linked-files/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-remark-copy-linked-files)

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

Author: dependabot[bot]