This Icon appears in the Utility bar. We can change this icon from choosing other lightning design system utility icon.Please follow the below steps to change the utility icon.
Steps to change the icon as below,
The Utility Icon changed successfully,
Image of Sales App Utility icon After change as below,
You can change the utility icon when you create the utility bar or else you can change it after creation of utility bar.
Some utilities don’t let you change icons. Like,