sql: allow CLOSE CURSOR in read-only txns

This is allowed in PG, so we now will allow this too. The fix is similar
to what we did for DECLARE and FETCH in 50a7999.

Release note (bug fix): CLOSE CURSOR statements are now allowed in
read-only transactions, similat to Postgres. The bug has been present
since at least 23.1 version.

pkg/sql/logictest/testdata/logic_test/txn

@@ -1520,13 +1520,16 @@ SET SESSION AUTHORIZATION DEFAULT
 statement ok
 BEGIN
 
-# DECLARE and FETCH CURSOR should work in a read-only txn.
+# DECLARE, FETCH, and CLOSE CURSOR should work in a read-only txn.
 statement ok
 DECLARE foo CURSOR FOR SELECT 1
 
 statement ok
 FETCH 1 foo
 
+statement ok
+CLOSE foo
+
 statement ok
 COMMIT
 

pkg/sql/sem/tree/stmt.go

@@ -768,7 +768,7 @@ func (*CannedOptPlan) StatementTag() string { return "PREPARE AS OPT PLAN" }
 func (*CloseCursor) StatementReturnType() StatementReturnType { return Ack }
 
 // StatementType implements the Statement interface.
-func (*CloseCursor) StatementType() StatementType { return TypeDCL }
+func (*CloseCursor) StatementType() StatementType { return TypeDML }
 
 // StatementTag returns a short string identifying the type of statement.
 func (*CloseCursor) StatementTag() string { return "CLOSE" }