Hey Diego,
This cannot be overridden using a child theme as we don’t have an API for this.
You need to edit the parent theme directly, which is not recommended. I’ll point you to the file but we cannot provide further support nor improvements for this.
Go to \themes\pro\cornerstone\includes\classes\styling and open the class-font-manager.php in a text editor.
Look for this line of code:
$buffer .= "@font-face { font-family: $family; font-display: $display; src: $sources; font-weight: $weight; font-style: $style; }";
Change the font-style value to normal or any other valid value you wish.
