Documentation specify layer name while Layer object is expected

### Description of the modifications

https://edb.core.docs.pyansys.com/version/stable/api/_autosummary/ansys.edb.core.layer.layer_collection.LayerCollection.add_layer_top.html#ansys.edb.core.layer.layer_collection.LayerCollection.add_layer_top

When we pass the layer name we got str doesn't have msg, we actually need to pass a StackupLayer object.

### Useful links and references

_No response_

Start with the linked API documentation for LayerCollection.add_layer_top and inspect how the layer parameter is described. Update the documentation to state that a StackupLayer object is expected rather than a layer name, then verify the rendered parameter description matches the method behavior.

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