Comment out the test_helpers module in lib.rs, indicating its use in fsrs-browser.

Author: L-M-Sherlock

src/lib.rs

@@ -10,7 +10,7 @@ mod model;
 mod parameter_clipper;
 mod parameter_initialization;
 mod simulation;
-#[cfg(test)]
+//#[cfg(test)] this module is used in fsrs-browser
 mod test_helpers;
 mod training;