Bump gatsby-remark-copy-linked-files from 6.14.0 to 6.15.0 (#1204)

Bumps [gatsby-remark-copy-linked-files](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-copy-linked-files) from 6.14.0 to 6.15.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-remark-copy-linked-files/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-remark-copy-linked-files@6.15.0/packages/gatsby-remark-copy-linked-files)

---
updated-dependencies:
- dependency-name: gatsby-remark-copy-linked-files
  dependency-version: 6.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]

package-lock.json

@@ -23,7 +23,7 @@
     "gatsby-plugin-offline": "6.14.0",
     "gatsby-plugin-sharp": "5.15.0",
     "gatsby-plugin-typography": "5.14.0",
-    "gatsby-remark-copy-linked-files": "6.14.0",
+    "gatsby-remark-copy-linked-files": "6.15.0",
     "gatsby-remark-images": "7.14.0",
     "gatsby-remark-prismjs": "7.15.0",
     "gatsby-remark-responsive-iframe": "6.14.0",