Update preview-sdks.yml

Author: fern-support

.github/workflows/preview-sdks.yml

@@ -31,8 +31,8 @@ jobs:
           FERN_TOKEN: ${{ secrets.FERN_TOKEN }}
         run: |
           cd fern/apis/api/.preview/fern-typescript-sdk
-          yarn install
-          yarn build
+          pnpm install
+          pnpm build
 
   preview-python:
     runs-on: ubuntu-latest