Remove spurrious space added in TClassEdit::ResolveTypedef

This solves ROOT-5778 by making sure that
 TClassEdit::ResolveTypedef("const std::string&")
and
 TClassEdit::ResolveTypedef("const std::string &")
returns "const std::string&"

This is a redo of 32df5a03fe2371d9ac46380ea6163d0519bbf711
which was inadvertently removed in 3d8b0cd4d0a3708885bd75e98d4b972a751a0a67