[Server] GetStyles: no more needs to add units in SLD

After @aaime works on SLD, no more needs to add units in SLD send by GetStyles

Author: rldhont

src/server/qgswmsprojectparser.cpp

@@ -1821,7 +1821,6 @@ QDomDocument QgsWMSProjectParser::getStyles( QStringList& layerList ) const
   // Create the root element
   QDomElement root = myDocument.createElementNS( "http://www.opengis.net/sld", "StyledLayerDescriptor" );
   root.setAttribute( "version", "1.1.0" );
-  root.setAttribute( "units", "mm" ); // default qgsmaprenderer is Millimeters
   root.setAttribute( "xsi:schemaLocation", "http://www.opengis.net/sld http://schemas.opengis.net/sld/1.1.0/StyledLayerDescriptor.xsd" );
   root.setAttribute( "xmlns:ogc", "http://www.opengis.net/ogc" );
   root.setAttribute( "xmlns:se", "http://www.opengis.net/se" );