@DoNotCall triggers a warning on default interface methods

Sample code below, it produces the following error:
```
error: [DoNotCall] Methods annotated with @DoNotCall should be final or static
```
It's an interface method so it can't be final or static. Adding `@SuppressWarnings("DoNotCall")` on the method does silence the error, so that's a workaround.
```
import com.google.errorprone.annotations.DoNotCall;

public interface Test {
@DoNotCall
default void foo() {}
}
```