Fix max-width on img for entity-print.css

If you add an image field to an Entity, upload a sufficiently large image to the entity, and check the export, you'll see that it doesn't respect the padding: 20px. Check on a mobile viewport if you don't notice on your standard desktop/laptop viewport. I came up with 2 lines of CSS to fix the issue for my case. I think that there are probably other HTML elements that will face this issue. If someone who has more front-end experience has a more sophisticated solution and/or wants to provide a list of other HTML elements that face this issue (if there are any), that would be awesome.