What happened to Assert.DoesNotThrowAsync() in xUnit?

I just wanted to update the answer with current information (Sep 2019).

As Malcon Heck mentioned, using the Record class is preferred. Looking at xUnit's Github, I see that a current way to check for lack of exceptions thrown is like this

[Fact]
public async Task CanDeleteAllTempFiles() {
    var exception = await Record.ExceptionAsync(() => DocumentService.DeleteAllTempDocuments());
    Assert.Null(exception);
}

As you can see in this discussion, the recommended way to test if a method does not throw in xUnit v2 is to just call it.

In your example, that would be:

[Fact]
public async Task CanDeleteAllTempFiles() {
    await DocumentService.DeleteAllTempDocuments();
}