gh-144173: fix flaky test_complex.test_truediv() (#144355)

Previously, component-wise relative error bound was tested.  However,
such bound can't exist already for complex multiplication as one can be
used to perform subtraction of floating-point numbers, e.g. x and y for
z0=1+1j and z1=x+yj.

```pycon
>>> x, y = 1e-9+1j, 1+1j
>>> a = x*y*y.conjugate()/2;a
(1.0000000272292198e-09+1j)
>>> b = x*(y*y.conjugate()/2);b
(1e-09+1j)
>>> b == x
True
>>> (a.real-b.real)/math.ulp(b.real)
131672427.0
```