Remove ResultsCursor::contains.

It's hardly worth it, and it needs to be removed so that
`GenKillAnalysis` can be removed.

clippy_utils/src/mir/possible_borrower.rs

@@ -213,7 +213,7 @@ impl<'b, 'tcx> PossibleBorrowerMap<'b, 'tcx> {
         self.bitset.0.clear();
         let maybe_live = &mut self.maybe_live;
         if let Some(bitset) = self.map.get(&borrowed) {
-            for b in bitset.iter().filter(move |b| maybe_live.contains(*b)) {
+            for b in bitset.iter().filter(move |b| maybe_live.get().contains(*b)) {
                 self.bitset.0.insert(b);
             }
         } else {
@@ -238,6 +238,6 @@ impl<'b, 'tcx> PossibleBorrowerMap<'b, 'tcx> {
 
     pub fn local_is_alive_at(&mut self, local: mir::Local, at: mir::Location) -> bool {
         self.maybe_live.seek_after_primary_effect(at);
-        self.maybe_live.contains(local)
+        self.maybe_live.get().contains(local)
     }
 }