How to remove underline from the text in a button?

Summary:

Our issue is about the text shown into buttons in a pop-up window, it most of the times is underlined.

Content:

Hi, we would like to know how to remove the underline from the text in the buttons that appear into the pop-up message windows, like when we submit data that need an approval flow, or when we send an incomplete evaluation in a performance document:

We didn't do any customization on these buttons.

How can we fix this?