Can't override `default-filter-lang` if it is set to `cql-json`

[mmcfarland]

If the pgstac_settings default-filter-lang is set to cql-json, I don't believe it can be overridden as intended by this line:

pgstac/sql/004_search.sql

Line 651 in 3afa5df

IF (search ? 'filter-lang' AND search->>'filter-lang' = 'cql-json') OR get_setting('default-filter-lang', _search->'conf')='cql-json' THEN

In the case where the default is set to "cql-json" and the client sends a filter-lang property of "cql2-json", I read the logic of that lines as (false or true) and it then attempts and fails to parse the cql2 as cql (which is the behavior I'm seeing). Instead, I think the default just need to be checked is the search didn't provide a filter-lang property.

If the default is set to cql2-json, the search-supplied and override behavior seems correct.