Fixed the partner logo grid breaking the About page on mobile

An image-sizing setting meant to make each logo scale down to fit its column was accidentally telling the browser to use each logo's original, much larger size instead. That was invisible on a wide desktop screen where there was room to spare, but on a phone-width screen it forced the two-column grid wider than the viewport, breaking the layout and forcing the whole page to scroll sideways.

The logos now correctly fill their grid column at every screen size, with the same two-columns-on-mobile, four-columns-on-desktop layout as before. There is no visual change beyond fixing the overflow.