Change size of Testimonial Image remove cropping

Hello, I’m trying to change the testimonial image size to 100px width and height, But when I upload the image in the testimonial, it crops the image to 60 x 60 making the image blurry at 100px. How do I remove the upload cropping 60 x 60 or change it to 100 x 100? Kindly advise, thanks.