Bump gatsby-plugin-image from 3.14.0 to 3.15.0

Bumps [gatsby-plugin-image](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-image) from 3.14.0 to 3.15.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-image/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-plugin-image)

---
updated-dependencies:
- dependency-name: gatsby-plugin-image
  dependency-version: 3.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -17,7 +17,7 @@
     "gatsby": "5.15.0",
     "gatsby-plugin-feed": "5.14.0",
     "gatsby-plugin-google-gtag": "5.14.0",
-    "gatsby-plugin-image": "3.14.0",
+    "gatsby-plugin-image": "3.15.0",
     "gatsby-plugin-manifest": "5.14.0",
     "gatsby-plugin-mdx": "5.14.1",
     "gatsby-plugin-offline": "6.14.0",