Bump babel-preset-gatsby from 3.13.0 to 3.13.1

Bumps [babel-preset-gatsby](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/babel-preset-gatsby) from 3.13.0 to 3.13.1.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/babel-preset-gatsby/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/babel-preset-gatsby@3.13.1/packages/babel-preset-gatsby)

---
updated-dependencies:
- dependency-name: babel-preset-gatsby
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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