ObservedTime to become optional

<?xml version="1.0" encoding="utf-8"?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"

           xmlns="urn:3GPP:ns:li:3GPPLIQueryExtensions:r18:v2"

           xmlns="urn:3GPP:ns:li:3GPPLIQueryExtensions:r18:v3"

           xmlns:x1="http://uri.etsi.org/03221/X1/2017/10"

           xmlns:common="http://uri.etsi.org/03280/common/2017/07"

           xmlns:etsi103120common="http://uri.etsi.org/03120/common/2016/02/Common"

           targetNamespace="urn:3GPP:ns:li:3GPPLIQueryExtensions:r18:v2"

           targetNamespace="urn:3GPP:ns:li:3GPPLIQueryExtensions:r18:v3"

           elementFormDefault="qualified">

  <xs:import namespace="http://uri.etsi.org/03221/X1/2017/10"/>

  <xs:complexType name="RequestDetails">

    <xs:sequence>

      <xs:element name="Type" type="DictionaryEntry"/>

      <xs:element name="ObservedTime" type="common:QualifiedDateTime"/>

      <xs:element name="ObservedTime" type="common:QualifiedDateTime" minOccurs="0"/>

      <xs:element name="RequestValues" type="RequestValues"/>

    </xs:sequence>

  </xs:complexType>