build(deps): bump gatsby-plugin-sharp from 2.6.40 to 2.11.2 in /docs

Bumps [gatsby-plugin-sharp](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-sharp) from 2.6.40 to 2.11.2.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/gatsby-plugin-sharp@2.11.2/packages/gatsby-plugin-sharp/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-sharp@2.11.2/packages/gatsby-plugin-sharp)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]