pgwire: CALL statement is returning RowDescription messages

When executing the CALL command, CockroachDB returns RowDescription messages. PostgreSQL does not return RowDescription messages after CALL commands.

Here's a pgwire test that shows the behavior:

```
# Create the test table
send
Query {"String": "CREATE TABLE mn (m INT PRIMARY KEY, n INT)"}
----

until
ReadyForQuery
----
{"Type":"CommandComplete","CommandTag":"CREATE TABLE"}
{"Type":"ReadyForQuery","TxStatus":"I"}

# Create PLpgSQL stored procedure that:
# 1. Takes an integer parameter as base value
# 2. Inserts a row using the parameter
# 3. Commits the transaction
# 4. Inserts another row using parameter + 1000
send
Query {"String": "CREATE OR REPLACE PROCEDURE p(base_val INT) LANGUAGE plpgsql AS $$ BEGIN INSERT INTO mn VALUES (base_val, base_val * 10); COMMIT; INSERT INTO mn VALUES (base_val + 1000, (base_val + 1000) * 10); END $$"}
----

until
ReadyForQuery
----
{"Type":"CommandComplete","CommandTag":"CREATE PROCEDURE"}
{"Type":"ReadyForQuery","TxStatus":"I"}

# Execute the stored procedure using simple query protocol
send
Query {"String": "CALL p(1)"}
----

until
ReadyForQuery
----
{"Type":"RowDescription","Fields":null}
{"Type":"RowDescription","Fields":null}
{"Type":"CommandComplete","CommandTag":"CALL"}
{"Type":"ReadyForQuery","TxStatus":"I"}
```

When watching the same sequence of commands sent to PostgreSQL 16.9 with Wireshark, it does not return RowDescription messages after the CALL statement.

Jira issue: CRDB-53274