Update package.json

Author: LB

packages/gatsby-plugin-theme-ui/package.json

@@ -7,7 +7,6 @@
   "peerDependencies": {
     "gatsby": "^2.13.1",
     "theme-ui": "^0.3.0",
-    "@theme-ui/prism": "0.3.0",
     "gatsby-core-utils": "^1.2.0"
   },
   "keywords": [