In salesforce when an approval process assigns an approval request to a user, Salesforce automatically sends the user an approval request email. When no email template is specified, a standard “out of the box” emails is sent. We are going see, how to disable standard Approval Process notifications in this blog
As an admin, We can’t disable the standard approval request email from being sent.
We can update the user’s record to prevent the user from getting the emails by setting the ‘Receive Approval Request Emails’ field to ‘Never’. With the field set to ‘Never’, you would create a workflow rule to generate emails.
Step1: in setup search for the User in search box.
Step2: Once selected the user in user list, need to click edit.
Step3: Under the ‘Receive Approval Request Emails’ field, select “Never” in the picklist.
Step4: Finally we can save. Now salesforce will not send approval process notification.
For Lightning :
Step1: Click the Gear icon then go to Setup | Administration | Users
Step2: Select any user, then click Edit button
Step3: Under ‘Receive Approval Request Emails’ field, select “Never”
Step4: Finally save
Click here for more : How to Create a Dynamic Actions Bar in Salesforce
For reference : Link