fix(deps): update gatsby monorepo

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby (changelog)	dependencies	minor	2.24.92 -> 2.25.0
gatsby-plugin-google-analytics	dependencies	minor	2.3.19 -> 2.4.0
gatsby-plugin-manifest	dependencies	minor	2.4.37 -> 2.5.0
gatsby-plugin-netlify	dependencies	minor	2.3.25 -> 2.4.0
gatsby-plugin-offline	dependencies	minor	3.2.38 -> 3.3.0
gatsby-plugin-sass	dependencies	minor	2.3.22 -> 2.4.0
gatsby-plugin-sharp	devDependencies	minor	2.6.44 -> 2.7.0
gatsby-remark-autolink-headers	dependencies	minor	2.3.16 -> 2.4.0
gatsby-remark-images	dependencies	minor	3.3.40 -> 3.4.0
gatsby-remark-prismjs	dependencies	minor	3.5.16 -> 3.6.0
gatsby-source-filesystem	dependencies	minor	2.3.37 -> 2.4.0
gatsby-transformer-remark	dependencies	minor	2.8.47 -> 2.9.0

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Release Notes

gatsbyjs/gatsby

### [`v2.25.0`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.24.92...gatsby@2.25.0) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.24.92...gatsby@2.25.0)

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[codecov-io]

Codecov Report

Merging #1145 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1145   +/-   ##
=======================================
  Coverage   75.25%   75.25%           
=======================================
  Files          15       15           
  Lines         295      295           
  Branches       80       80           
=======================================
  Hits          222      222           
  Misses         68       68           
  Partials        5        5           

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