Call stack tests break if `main.dart` in `fixtures/_testPackageSound` / `fixtures/_testPackage` is formatted

[elliette]

We should fix the tests so that they pass when the file is formatted.

[jyameo]

Formatting fixtures/_testPackageSound/web/main.dart doesn't seem to cause any breakage. I've verified that no changes occur after applying dart format, so I'll go ahead and close this issue.