remove features if present in model

[Kr0nox]

If the features are present on a model after loading, they do not have an underlying implementation. This leads to errors when trying to display the diagram.
Previously this was solved by this

WebEditor/src/features/serialize/load.ts

Lines 253 to 256 in 6b84cc2

	public static preprocessModelSchema(modelSchema: SModelRoot): void {
	// These properties are all not included in the root typing.
	"features" in modelSchema && delete modelSchema["features"];
	"canvasBounds" in modelSchema && delete modelSchema["canvasBounds"];

#98 falsely removed these lines.

They are now added again in an easier to read method and longer explanation