removing postbuild task (#1630)

Author: gloriachen

storybook/package.json

@@ -7,8 +7,7 @@
   "scripts": {
     "start": "start-storybook  -c .storybook -p 3333  --host 0.0.0.0",
     "develop": "export storybookBuildMode=develop && yarn start",
-    "build": "build-storybook -c .storybook",
-    "postbuild": "npx sb extract"
+    "build": "build-storybook -c .storybook"
   },
   "dependencies": {
     "@looker/components": "^0.9.22",