Xpath | Change @codeListValue

Question

I have the following XML snippet, referring to a metadata published in my GeoNetwork:

<mri:spatialRepresentationType>
  <mcc:MD_SpatialRepresentationTypeCode codeList="http://standards.iso.org/iso/19115/resources/Codelists/cat/codelists.xml#MD_SpatialRepresentationTypeCode" codeListValue="grid"/>
</mri:spatialRepresentationType>

I would like to change the @codeListValue="grid" to "Matricial" using the advanced (XPath) mode of GeoNetwork (3.10.2), but I believe that I not been able to create the appropriate XPath.