Use higher relative tolerance in SqueezedSparseConversion tests (#1710)
Use higher relative tolerance in SqueezedSparseConversion tests (#1710)

These tests seem to be failing occasionally (for instance, 3 failures across a
few hundred runs locally), probably due to the changing thresholds in
#1679. These tests are slightly numerically unstable, and so `assert_allclose`'s
default relative threshold of 1e-7 is too small. In fact, this is less than the
precision of a float32, meaning if `abs(a - b) > atol` (where `atol = 1e-7`),
then the test will fail unless `a == b` exactly.

This patch changes the relative tolerance for these tests back to `rtol = 1e-5`
to match the `np.allclose` function. Defaults for each function:

| function          | `rtol` | `atol` |
|-------------------|--------|--------|
| `allclose`        | 1e-5   | 1e-8   |
| `assert_allclose` | 1e-7   | 0      |


Docs:

- https://numpy.org/doc/stable/reference/generated/numpy.allclose.html
- https://numpy.org/doc/stable/reference/generated/numpy.testing.assert_allclose.html

I "verified" this by running each of the three tests 1000 times locally.

See: #1709

stellargraph/stellargraph,stellargraph/stellargraph