Fix image preview within Media Library modal

The Claro admin theme doesnt exhibit any problems here because of the responsive img css styles in elements.css:

img {
    max-width: 100%;
    height: auto;
}

I'm tempted to close this as outdated unless someone can provide steps to reproduce using an admin theme, e.g., one that doesn't support responsive images out of the box maybe??? And even in that case, the proper fix will require creating an upstream issue on the admin theme's queue to support responsive images in the Media Library preview form widget. :)

I'm almost 100% certain we do not want to get into display inline SVGs in this preview form, as the current MR approach takes.