remove outdated TODO markers

These were left behind to remind me to cleanup the code -- but the
relevant cleanups were already done.

src/librustc_mir/borrow_check/nll/pick_constraints.rs

-#![allow(dead_code)] // TODO
-
 use crate::rustc::ty::{self, Ty};
 use rustc::hir::def_id::DefId;
 use rustc::infer::region_constraints::PickConstraint;

src/librustc_mir/borrow_check/nll/region_infer/mod.rs

@@ -1486,7 +1486,7 @@ fn check_pick_constraints(
         &self,
         infcx: &InferCtxt<'_, 'tcx>,
         mir_def_id: DefId,
-        errors_buffer: &mut Vec<Diagnostic>, // TODO
+        errors_buffer: &mut Vec<Diagnostic>,
     ) {
         let pick_constraints = self.pick_constraints.clone();
         for p_c_i in pick_constraints.all_indices() {