Remove deprecated byte_update_exprt non-const methods

They were deprecated in 2019 in favour of their set_* counterparts, and
had no in-tree users left.

Author: tautschnig

src/util/byte_operators.h

@@ -92,13 +92,6 @@ class byte_update_exprt : public ternary_exprt
       "byte_update_exprt: Invalid ID");
   }
 
-  DEPRECATED(SINCE(2019, 5, 21, "use set_op or as_const instead"))
-  exprt &op() { return op0(); }
-  DEPRECATED(SINCE(2019, 5, 21, "use set_offset or as_const instead"))
-  exprt &offset() { return op1(); }
-  DEPRECATED(SINCE(2019, 5, 21, "use set_value or as_const instead"))
-  exprt &value() { return op2(); }
-
   void set_op(exprt e)
   {
     op0() = std::move(e);