Redundant lines in maxlambda.f90

The lines below in https://github.com/jstriaukas/midasml/blob/master/src/maxlambda.f90 are redundant.

```
    IF (nzvars .NE. 0) THEN
        !CALL rnz(nvars, nobs, nzvars, y, x, r, pf)
    END IF
```