Explicit string type correction

Signed-off-by: Steve Springett <steve@springett.us>

Author: stevespringett

schema/bom-1.6.xsd

@@ -7177,7 +7177,7 @@ limitations under the License.
                                 </xs:restriction>
                             </xs:simpleType>
                         </xs:element>
-                        <xs:element name="version" minOccurs="0" maxOccurs="1">
+                        <xs:element name="version" type="xs:string" minOccurs="0" maxOccurs="1">
                             <xs:annotation>
                                 <xs:documentation>
                                     The version of the protocol. Examples include 1.0, 1.2, and 1.99.