BUG #17294: spgist doesn't support varchar, only text type fields.

The following bug has been logged on the website:

Bug reference:      17294
Logged by:          Ilya Anfimov
Email address:      ilan@tzirechnoy.com
PostgreSQL version: 14.1
Operating system:   Devuan GNU/linux beowulf
Description:

I found that on 14.0 and 14.1 the server gives the error when I try to
create spgist index on a varchar field.
Note, that on 9.4 - 13 servers this test worked fine.

ilank=*> create table test (a text, b varchar);
CREATE TABLE
ilank=*> create index on test using spgist (a);
CREATE INDEX
ilank=*> create index on test using spgist (b);
ERROR:  compress method must be defined when leaf type is different from
input type