Improve coverage on ``shapes`` subpackage

[RobPasMue]

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See https://app.codecov.io/gh/ansys/pyansys-geometry/tree/main/src%2Fansys%2Fgeometry%2Fcore%2Fshapes

Looks like the shapes subpackage is know partially covered. Let's try to reach as close to 100% as possible. If there are "unaccessible" statements, you can add # pragma: no cover to them. See other examples in the library.