don't write this default attribute

"preserve" is the default value and the OOXML spec sadly does not
contain the definition for xml:space. It is only mentioned in the
documentation so validation against the schema file fails.

Change-Id: I53f804e189dca585fceb4474b96b1b4536d5bde4

sc/source/filter/excel/xestring.cxx

@@ -403,7 +403,6 @@ static sal_uInt16 lcl_WriteRun( XclExpXmlStream& rStrm, const ScfUInt16Vec& rBuf
         rWorksheet->endElement( XML_rPr );
     }
     rWorksheet->startElement( XML_t,
-            FSNS( XML_xml, XML_space ), "preserve",
             FSEND );
     rWorksheet->writeEscaped( XclXmlUtils::ToOUString( rBuffer, nStart, nLength ) );
     rWorksheet->endElement( XML_t );