Update gatsby monorepo

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby-plugin-sharp	dependencies	patch	2.3.0 -> 2.3.1
gatsby-transformer-remark	dependencies	patch	2.6.35 -> 2.6.36

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Release Notes

gatsbyjs/gatsby

### [`v2.3.1`](https://togithub.com/gatsbyjs/gatsby/compare/2f4c4608df62e867f646881a00a5141860b7f5e0...53e34a58d25ef29567875bdbdb5871b0718ce61c) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/1e6954a0e8e8a661a58bc3421a3d17d8e38e766c...314526e2bc28715d83ffde0e6c172b483db1184c)

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[codecov[bot]]

Codecov Report

Merging #355 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #355   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           5      5           
  Lines          60     60           
  Branches       10     10           
=====================================
  Hits           60     60

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