Fixed error range for s4s-elt-invalid-content.3

[angelozerr]

With the given XSD file:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
	<xs:element name="project" type="xs:string"></xs:element>
	<xs:import ></xs:import>
</xs:schema>

xs:import should be higlighted as error with message:

s4s-elt-invalid-content.3: Elements of type 'import' cannot appear after declarations as children of a <schema> element.

We could add a code action to remove this xs:import element.