Fix indentation in addMathMLAsCompleteXMLDoc expected output.
Fix indentation in addMathMLAsCompleteXMLDoc expected output.

nickerso/libcellml,nickerso/libcellml,nickerso/libcellml,nickerso/libcellml,cellml/libcellml,cellml/libcellml,cellml/libcellml,cellml/libcellml