fix(deps): update gatsby

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
gatsby	dependencies	patch	^2.15.28 -> ^2.15.29
gatsby-link	dependencies	patch	^2.2.17 -> ^2.2.18
gatsby-plugin-netlify-cms	dependencies	patch	^4.1.21 -> ^4.1.22
gatsby-plugin-sharp	dependencies	patch	^2.2.27 -> ^2.2.28
gatsby-remark-copy-linked-files	dependencies	patch	^2.1.23 -> ^2.1.24
gatsby-remark-prismjs	dependencies	patch	^3.3.16 -> ^3.3.17
gatsby-remark-responsive-iframe	dependencies	patch	^2.2.20 -> ^2.2.21
gatsby-source-filesystem	dependencies	patch	^2.1.28 -> ^2.1.29
gatsby-transformer-remark	dependencies	patch	^2.6.26 -> ^2.6.27
gatsby-transformer-sharp	dependencies	patch	^2.2.19 -> ^2.2.20

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Release Notes

gatsbyjs/gatsby

v2.15.29

Compare Source

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     fix(deps): update gatsby

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