Change copyright statements from 2020 to 2021

v3_20_0/CDT-cmdhDefEcValue-v3_20_0.xsd

v3_20_0/CDT-cmdhDefaults-v3_20_0.xsd

v3_20_0/CDT-cmdhEcDefParamValues-v3_20_0.xsd

v3_20_0/CDT-cmdhLimits-v3_20_0.xsd

v3_20_0/CDT-cmdhNetworkAccessRules-v3_20_0.xsd

v3_20_0/CDT-cmdhNwAccessRule-v3_20_0.xsd

v3_20_0/CDT-cmdhPolicy-v3_20_0.xsd

v3_20_0/CDT-commonTypes-v3_20_0.xsd

v3_20_0/CDT-container-v3_20_0.xsd

v3_20_0/CDT-contentInstance-v3_20_0.xsd

v3_20_0/CDT-crossResourceSubscription-v3_20_0.xsd

v3_20_0/CDT-delivery-v3_20_0.xsd

v3_20_0/CDT-deviceCapability-v3_20_0.xsd

v3_20_0/CDT-deviceInfo-v3_20_0.xsd

v3_20_0/CDT-dynamicAuthorizationConsultation-v3_20_0.xsd

v3_20_0/CDT-enumerationTypes-v3_20_0.xsd

v3_20_0/CDT-eventConfig-v3_20_0.xsd

v3_20_0/CDT-eventLog-v3_20_0.xsd

v3_20_0/CDT-execInstance-v3_20_0.xsd

v3_20_0/CDT-firmware-v3_20_0.xsd