Once you have created a feed rule or a draft rule in Google Merchant, you can always delete them in your data feed rules tab.
Login to Google Merchant
Select your feed
Go to Products > Feeds > Click on your feed
Select your feed rule
Go to Rules > Select your rule
Deleting a feed rule
Click on the arrow drop down > click on the 3dot menu > Delete rule
Applying the changes
Click on Apply to confirm the new changes