sql: SHOW CREATE TABLE incorrectly shows an opclass for non-inverted prefix columns of trigram index

[mgartner]

Notice how the first column in the secondary index has an opclass below. That is incorrect.

defaultdb> CREATE TABLE t (a INT, s STRING, INVERTED INDEX (a, s gist_trgm_ops));
CREATE TABLE

defaultdb> SHOW CREATE TABLE t;
  table_name |                         create_statement
-------------+--------------------------------------------------------------------
  t          | CREATE TABLE public.t (
             |     a INT8 NULL,
             |     s STRING NULL,
             |     rowid INT8 NOT VISIBLE NOT NULL DEFAULT unique_rowid(),
             |     CONSTRAINT t_pkey PRIMARY KEY (rowid ASC),
             |     INVERTED INDEX t_a_s_idx (a gin_trgm_ops ASC, s gin_trgm_ops)
             | )
(1 row)

Related to #84512.

Jira issue: CRDB-18839