fix(deps): update gatsby

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby	dependencies	patch	^2.15.28 -> ^2.15.29
gatsby-image	dependencies	patch	^2.2.23 -> ^2.2.24
gatsby-plugin-google-analytics	dependencies	patch	^2.1.19 -> ^2.1.20
gatsby-plugin-sharp	dependencies	patch	^2.2.27 -> ^2.2.28
gatsby-plugin-typography	dependencies	patch	^2.3.10 -> ^2.3.11
gatsby-transformer-sharp	dependencies	patch	^2.2.19 -> ^2.2.20

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Release Notes

gatsbyjs/gatsby

### [`v2.15.29`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.15.28...gatsby@2.15.29) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.15.28...gatsby@2.15.29)

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