fix(deps): update dependency gatsby to v2.25.4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby (changelog)	dependencies	patch	2.25.3 -> 2.25.4

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Release Notes

gatsbyjs/gatsby

### [`v2.25.4`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.25.3...gatsby@2.25.4) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.25.3...gatsby@2.25.4)

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[codecov-io]

Codecov Report

Merging #1156 (d835183) into master (e463bee) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1156   +/-   ##
=======================================
  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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