Bump gatsby-plugin-react-helmet from 3.1.7 to 3.1.8

Bumps [gatsby-plugin-react-helmet](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-react-helmet) from 3.1.7 to 3.1.8.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-react-helmet/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-react-helmet@3.1.8/packages/gatsby-plugin-react-helmet)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

package.json

@@ -11,7 +11,7 @@
     "gatsby-plugin-manifest": "^2.2.18",
     "gatsby-plugin-offline": "^3.0.6",
     "gatsby-plugin-postcss": "^2.1.8",
-    "gatsby-plugin-react-helmet": "^3.1.7",
+    "gatsby-plugin-react-helmet": "^3.1.8",
     "gatsby-plugin-sharp": "^2.2.25",
     "gatsby-source-filesystem": "^2.1.22",
     "gatsby-transformer-sharp": "^2.2.16",

yarn.lock

@@ -5214,10 +5214,10 @@ gatsby-plugin-postcss@^2.1.8:
     "@babel/runtime" "^7.6.0"
     postcss-loader "^3.0.0"
 
-gatsby-plugin-react-helmet@^3.1.7:
-  version "3.1.7"
-  resolved "https://registry.yarnpkg.com/gatsby-plugin-react-helmet/-/gatsby-plugin-react-helmet-3.1.7.tgz#f93770eef0a7a6692249cc6437e11dda2729e1fa"
-  integrity sha512-mW5t8Fu2taX1azf5hnidj565HSFgBPaBzpxyprqhdIPWANh+Er+eA9x9Pz+c3Tw33ia2aghKTzocHa5pYTu0KA==
+gatsby-plugin-react-helmet@^3.1.8:
+  version "3.1.8"
+  resolved "https://registry.yarnpkg.com/gatsby-plugin-react-helmet/-/gatsby-plugin-react-helmet-3.1.8.tgz#319254fd8cd99d0fcd615cee11a5d1f1ad0ab6f4"
+  integrity sha512-EpBpTwRLOHrxQLL9D3pBikgtW/4TIeUbZc93raerLr14ihht6wdWcGs4pjYAt0cKhRJ2WCvk3pgC3/yM6CEDww==
   dependencies:
     "@babel/runtime" "^7.6.0"