Minor: Port tests in displayable.rs to sqllogictest (#8246)

* remove test file

* fix: update mod

Author: Weijun-H

datafusion/core/tests/sql/displayable.rs

@@ -76,7 +76,6 @@ pub mod aggregates;
 pub mod create_drop;
 pub mod csv_files;
 pub mod describe;
-pub mod displayable;
 pub mod explain_analyze;
 pub mod expr;
 pub mod group_by;