remove postinstall (#2037)

Author: rezrah

.github/workflows/deploy_preview.yml

@@ -14,5 +14,6 @@ jobs:
     uses: primer/.github/.github/workflows/deploy_preview.yml@main
     with:
       node_version: 16
+      install: npm ci && cd docs && npm ci && cd ..
       build: npm run build:docs:preview
       output_dir: docs/public

.github/workflows/deploy_production.yml

@@ -39,5 +39,6 @@ jobs:
     uses: primer/.github/.github/workflows/deploy.yml@main
     with:
       node_version: 16
+      install: npm ci && cd docs && npm ci && cd ..
       build: npm run build:docs
       output_dir: docs/public

package.json

@@ -49,7 +49,6 @@
     "test:type-check": "tsc --noEmit",
     "release": "npm run build && changeset publish",
     "size": "size-limit",
-    "postinstall": "cd docs && npm i",
     "prepare": "husky install"
   },
   "repository": "primer/react",