fix(deps): update gatsby

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby-plugin-netlify	dependencies	patch	^2.1.25 -> ^2.1.26
gatsby-plugin-sharp	dependencies	patch	^2.3.2 -> ^2.3.3

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Release Notes

gatsbyjs/gatsby

### [`v2.1.26`](https://togithub.com/gatsbyjs/gatsby/compare/e9c8e8a6628b1d325c5ae15ebbceec73cc1226e4...90ac3a5c80dc552ca687988602311914d8d9b193) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/e6a30aaadc6949d125eaf4d16c8fb36ebafad10d...787d9410e0baeeed29f74d0e93ed894e2ee6ce90)

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