How to Stop Google Apps Script

Duplicate with 10666.The timing was wrong, but 10666 was included in the close vote, so I will answer it as positive.

The script file is stored in Google drive.
https://drive.google.com/
Delete the script file.
If you're curious about the content, double-click and select Google Apps Script from
to go to the script editing page.

If you're worried, check your Google My Account Permissions
https://myaccount.google.com/
Connected apps and services > Account permissions.
If you select it, you will see the "revoke" button on the right.You can remove the permissions from there.
Also, if you delete the script file from Google drive.
It is also automatically removed from the permissions list.