You can remove synced files from your Chromebook by turning off your Google Drive.
Turn off Google Drive
- Make sure you are online, and login to your Chromebook.
- Open Chrome .
- Navigate to your Google Drive by going to drive.google.com.
- Click on the setting icon in the top right hand corner.
- From the offline area,uncheck the box next to:Sync Google Docs, Sheets, Slides & Drawing Files to this computer so that you can edit offline.
- Select Done.