Yes, you can. Orange is a garnish for the beer. As with all garnishes, it is not a must in the beer.
There is no doubt that orange accentuates the beer’s flavor. Note that, in general, the beer has a hint of citrus. The only purpose of adding an orange is for improving the flavor. In other words, you will still taste the citrus flavor even without the orange garnish. And some people may prefer it this way.