Hide author from search results meta, still display date and categories

As stated in my comment the best solution would be to create a child theme and edit the file generating the post meta. This would give you full control of what is being generated and you won’t have to worry about hiding unwanted content via CSS.

However, you could hide the text nodes and show the elements you want by doing something like this…

    .post-meta {
        visibility:collapse;
    }

    .published {
        visibility:visible;
    }

Note: The above hidden items will still keep their space in the DOM, so you could add float:left to .published to break the flow.