The Divi theme comes with a gallery module which lets you display images in both a grid and slider format. When clicked, the images will display in a pop-up "lightbox". If you'd like to disable this so that the images are not clickable and don't open in a popup, you can do it like so:

Disable Gallery Module Lightbox in the Module Settings

There isn't a specific setting for it, but you can disable the gallery module lightbox popup via the module settings by setting:

Gallery Settings > Advanced > Custom CSS > Gallery Item

To include the following:

Disable Gallery Module Lightbox using CSS

If you need to disable the gallery module lightbox popup using full CSS, you can do so by giving your gallery module an ID (such as "my-gallery-id") at:

Gallery Settings > Advanced > CSS ID & Classes > CSS ID

And then adding the following CSS to your site:

Related Post: Adding CSS to the Divi Theme