Remove ResultsCursor::contains.

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

compiler/rustc_mir_dataflow/src/framework/cursor.rs

@@ -7,7 +7,6 @@ use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::{self, BasicBlock, Location};
 
 use super::{Analysis, Direction, Effect, EffectIndex, Results};
-use crate::framework::BitSetExt;
 
 /// Allows random access inspection of the results of a dataflow analysis.
 ///
@@ -221,16 +220,6 @@ where
     }
 }
 
-impl<'mir, 'tcx, A> ResultsCursor<'mir, 'tcx, A>
-where
-    A: crate::GenKillAnalysis<'tcx>,
-    A::Domain: BitSetExt<A::Idx>,
-{
-    pub fn contains(&self, elem: A::Idx) -> bool {
-        self.get().contains(elem)
-    }
-}
-
 #[derive(Clone, Copy, Debug)]
 struct CursorPosition {
     block: BasicBlock,