sql: SHOW CREATE VIEW on materialized view should not show implicit rowid column

`SHOW CREATE VIEW` on a materialized view outputs a `CREATE MATERIALIZED VIEW` statement that includes the implicit `rowid` column, which causes an error when running the statement.

```defaultdb> CREATE MATERIALIZED VIEW v (i, j) AS (SELECT 1, 2);
CREATE VIEW

defaultdb> SELECT create_statement from [SHOW CREATE VIEW v];
create_statement
---------------------------------------
CREATE MATERIALIZED VIEW public.v (
i,
j,
rowid
) AS (SELECT 1, 2)
(1 row)

defaultdb> CREATE MATERIALIZED VIEW public.v (
i,
j,
rowid
) AS (SELECT 1, 2)
ERROR: CREATE VIEW specifies 3 column names, but data source has 2 columns
SQLSTATE: 42601
```

Jira issue: CRDB-25670