Remove set_config call from structure.sql

[tsujigiri]

It's blocking and doesn't really do anything, it seems.

[philippbayer]

Docs say:

If untrusted users have access to a database that has not adopted a secure schema usage pattern, begin each session by removing publicly-writable schemas from search_path. For example, add options=-csearch_path= to options, or issue EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); after connecting. This consideration is not specific to ECPG; it applies to every interface for executing arbitrary SQL commands.

So I think too that can go, as we don't have untrusted users

[tsujigiri]

It's only for testing, anyway.