Update dependency gatsby-plugin-sharp to v2.3.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby-plugin-sharp	dependencies	minor	2.2.39 -> 2.3.0

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Release Notes

gatsbyjs/gatsby

### [`v2.3.0`](https://togithub.com/gatsbyjs/gatsby/compare/868b44f5522edd3fd09fbe68aaa6e995e3cdfe03...2f4c4608df62e867f646881a00a5141860b7f5e0) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/e6a30aaadc6949d125eaf4d16c8fb36ebafad10d...1e6954a0e8e8a661a58bc3421a3d17d8e38e766c)

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[codecov[bot]]

Codecov Report

Merging #352 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #352   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           5      5           
  Lines          60     60           
  Branches       10     10           
=====================================
  Hits           60     60

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