Are you running on iOS < 13 and does one of your dependencies or other libraries offer async APIs? If so, the concurrency library is added, even if you never call the code. For example, anyone updating to Alamofire 5.5 will hit this since I added various async APIs for iOS 13 and above. It seems like it should just be stripped when deploying to older OSes, but I don't know if the solution is that simple.
Edit: Actually, you're likely seeing a different issue that the original one described here: Swift Concurrency back-deploy issue