fisher.c: fix typos in the documentation
fisher.c: fix typos in the documentation

erexhepa/vlfeat,qubick/vlfeat,rxl194/vlfeat,qubick/vlfeat,hongzhili/vlfeat,WangDequan/vlfeat,mylxiaoyi/vlfeat,CansenJIANG/vlfeat,richarddzh/vlfeat,hongzhili/vlfeat,CansenJIANG/vlfeat,hongzhili/vlfeat,j-bo/vlfeat,mylxiaoyi/vlfeat,vlfeat/vlfeat,richarddzh/vlfeat,WangDequan/vlfeat,cvfish/vlfeat,erexhepa/vlfeat,CansenJIANG/vlfeat,hongzhili/vlfeat,CansenJIANG/vlfeat,richarddzh/vlfeat,vlfeat/vlfeat,rxl194/vlfeat,richarddzh/vlfeat,WangDequan/vlfeat,richarddzh/vlfeat,j-bo/vlfeat,erexhepa/vlfeat,rxl194/vlfeat,WangDequan/vlfeat,hongzhili/vlfeat,cvfish/vlfeat,qubick/vlfeat,qubick/vlfeat,rxl194/vlfeat,vlfeat/vlfeat,j-bo/vlfeat,mylxiaoyi/vlfeat,rxl194/vlfeat,erexhepa/vlfeat,mylxiaoyi/vlfeat,qubick/vlfeat,WangDequan/vlfeat,CansenJIANG/vlfeat,richarddzh/vlfeat,cvfish/vlfeat,vlfeat/vlfeat,vlfeat/vlfeat,qubick/vlfeat,cvfish/vlfeat,hongzhili/vlfeat,erexhepa/vlfeat,mylxiaoyi/vlfeat,rxl194/vlfeat,cvfish/vlfeat,erexhepa/vlfeat,vlfeat/vlfeat,j-bo/vlfeat,j-bo/vlfeat,WangDequan/vlfeat,mylxiaoyi/vlfeat,CansenJIANG/vlfeat,cvfish/vlfeat