chore: remove unused code

Remove old PSQT code
bench: 1740232

Author: DeveloperPaul123

engine/src/lib.rs

@@ -6,7 +6,6 @@ pub mod hce_values;
 pub mod history_table;
 pub mod input_handler;
 pub mod phased_score;
-pub mod psqt;
 pub mod score;
 pub mod search;
 pub mod search_thread;