Remove unreachable code

Author: peterschrammel

src/goto-programs/goto_program.cpp

@@ -484,6 +484,4 @@ std::string as_string(
   default:
     throw "unknown statement";
   }
-
-  return "";
 }

src/solvers/sat/pbs_dimacs_cnf.cpp

@@ -255,7 +255,4 @@ tvt pbs_dimacs_cnft::l_get(literalt a) const
           return tvt(true);
         }
     }
-
-  // std::cout << "ERROR" << "\n";
-  return tvt::unknown();
 }