1. At the bottom right corner of your inbox, click on details as indicated in the image, to open the activity on your account popup window.
2. Click on Security checkup as shown by the arrow, to open the security checkup window.
3. Click on "Your devices".
4. At the bottom right corner, click on "Review devices" to view the different devices connected to your Gmail account.
5. Review and select the device to disconnect as shown in the image. (Pixel 6 Pro)
6. Click "Sign out".
7. Click on "Sign out" to confirm.