fix(deps): update gatsby

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby	dependencies	patch	^2.18.12 -> ^2.18.16
gatsby-image	dependencies	patch	^2.2.36 -> ^2.2.37
gatsby-plugin-manifest	dependencies	patch	^2.2.33 -> ^2.2.34
gatsby-plugin-offline	dependencies	patch	^3.0.29 -> ^3.0.30
gatsby-plugin-sharp	dependencies	patch	^2.3.7 -> ^2.3.10

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Release Notes

gatsbyjs/gatsby

### [`v2.18.16`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.15...gatsby@2.18.16) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.15...gatsby@2.18.16) ### [`v2.18.15`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.14...gatsby@2.18.15) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.14...gatsby@2.18.15) ### [`v2.18.14`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.13...gatsby@2.18.14) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.13...gatsby@2.18.14) ### [`v2.18.13`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.12...gatsby@2.18.13) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.12...gatsby@2.18.13)

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