remove an extraneous comment

Co-authored-by: Rémy Rakic <remy.rakic+github@gmail.com>

Author: dingxiangfei2009

Diff for: compiler/rustc_borrowck/src/lib.rs

@@ -1157,7 +1157,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
     ) {
         let sd = AccessDepth::Drop;
 
-        // Use polonius output if it has been enabled.
         let borrows_in_scope = self.borrows_in_scope(location, state);
 
         // This is a very simplified version of `Self::check_access_for_conflict`.