Types of changes

Tests on the first marginal within sr(F)GW solvers were not compatible with gpu usage as
np.testing.assert_allclose(nx.sum(G0, 1), p, atol=1e-08)
implies that variables are converted to numpy and stored on cpu before the test. This test fails if it requires first to move variables from gpu to cpu.

Fix: assert nx.allclose(nx.sum(G0, 1), p, atol=1e-08)

Motivation and context / Related issue

How has this been tested (if it applies)

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.