Address unstable test_ellipse_parameter_stability

[lagru]

The results of the tested code seem rather unstable depending on architecture or environment:

• Test failures on i386 #6995
• [0.21.0] test_ellipse_parameter_stability sometimes fails #7061
• some tests fail on aarch64 dawin #7104

Either figure out if we can make EllipseModel more stable or if the test can be made to test a more reliable property. As is this causes problems for downstream packagers.