fix: schema name escaping

[soedirgo]

schemaname::regnamespace only works if the name is already quoted - e.g. for a schema named MySchema, '"MySchema"'::regnamespace works but 'MySchema'::regnamespace doesn't. So we use %I formatting instead.

• sanity tested on stg:

create schema "MySchema";
alter default privileges for role postgres in schema "MySchema" grant all on tables to anon;