build(deps): bump gatsby-remark-copy-linked-files in /docs (#2545)

Bumps [gatsby-remark-copy-linked-files](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-copy-linked-files) from 5.4.0 to 5.6.0.
- [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/gatsby-remark-copy-linked-files@5.6.0/packages/gatsby-remark-copy-linked-files)

---
updated-dependencies:
- dependency-name: gatsby-remark-copy-linked-files
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]

docs/package-lock.json

@@ -27,7 +27,7 @@
     "gatsby-plugin-sharp": "^3.10.2",
     "gatsby-plugin-sitemap": "^5.6.0",
     "gatsby-remark-autolink-headers": "^2.11.0",
-    "gatsby-remark-copy-linked-files": "^5.4.0",
+    "gatsby-remark-copy-linked-files": "^5.6.0",
     "gatsby-remark-embedder": "^4.2.0",
     "gatsby-remark-external-links": "0.0.4",
     "gatsby-remark-images": "^3.11.1",