[doxygen] fix doxygen in binarycoefficents

dumux/material/binarycoefficients/CMakeLists.txt

dumux/material/binarycoefficients/air_mesitylene.hh

dumux/material/binarycoefficients/air_xylene.hh

dumux/material/binarycoefficients/brine_air.hh

dumux/material/binarycoefficients/brine_co2.hh

dumux/material/binarycoefficients/fullermethod.hh

dumux/material/binarycoefficients/h2o_air.hh

dumux/material/binarycoefficients/h2o_constant.hh

dumux/material/binarycoefficients/h2o_heavyoil.hh

dumux/material/binarycoefficients/h2o_mesitylene.hh

dumux/material/binarycoefficients/h2o_n2.hh

dumux/material/binarycoefficients/h2o_o2.hh

dumux/material/binarycoefficients/h2o_xylene.hh

dumux/material/binarycoefficients/henryiapws.hh

dumux/material/binarycoefficients/n2_o2.hh