build(deps): bump gatsby-plugin-sharp from 2.6.31 to 2.6.40 in /docs (#1423)

Bumps [gatsby-plugin-sharp](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-sharp) from 2.6.31 to 2.6.40.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-sharp/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-sharp@2.6.40/packages/gatsby-plugin-sharp)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

docs/package-lock.json

@@ -25,7 +25,7 @@
     "gatsby-plugin-react-helmet": "^3.3.10",
     "gatsby-plugin-react-svg": "^3.0.0",
     "gatsby-plugin-robots-txt": "^1.5.1",
-    "gatsby-plugin-sharp": "^2.6.31",
+    "gatsby-plugin-sharp": "^2.6.40",
     "gatsby-plugin-sitemap": "^2.4.14",
     "gatsby-remark-autolink-headers": "^2.3.13",
     "gatsby-remark-copy-linked-files": "^2.3.12",