fix grammar for SMT-LIB2 declare-fun

The grammar for the SMT-LIB 2 command declare-fun does not expect a
parameter identifier.

Author: kroening

src/solvers/smt2/smt2_parser.cpp

@@ -1223,19 +1223,8 @@ typet smt2_parsert::function_signature_declaration()
   mathematical_function_typet::domaint domain;
 
   while(smt2_tokenizer.peek() != smt2_tokenizert::CLOSE)
-  {
-    if(next_token() != smt2_tokenizert::OPEN)
-      throw error("expected '(' at beginning of parameter");
-
-    if(next_token() != smt2_tokenizert::SYMBOL)
-      throw error("expected symbol in parameter");
-
     domain.push_back(sort());
 
-    if(next_token() != smt2_tokenizert::CLOSE)
-      throw error("expected ')' at end of parameter");
-  }
-
   next_token(); // eat the ')'
 
   typet codomain = sort();