fix(deps): update dependency gatsby-theme-apollo-docs to v4.7.15 (#1907)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

docs/package-lock.json

@@ -8,7 +8,7 @@
   "dependencies": {
     "gatsby": "2.32.13",
     "gatsby-plugin-react-svg": "3.0.1",
-    "gatsby-theme-apollo-docs": "4.7.14",
+    "gatsby-theme-apollo-docs": "4.7.15",
     "react": "17.0.2",
     "react-dom": "17.0.2"
   }