Rollup merge of #111952 - cjgillot:drop-replace, r=WaffleLapkin

Remove DesugaringKind::Replace.

A simple boolean flag is enough.

compiler/rustc_span/src/hygiene.rs

@@ -1147,7 +1147,6 @@ pub enum DesugaringKind {
     Await,
     ForLoop,
     WhileLoop,
-    Replace,
 }
 
 impl DesugaringKind {
@@ -1163,7 +1162,6 @@ impl DesugaringKind {
             DesugaringKind::OpaqueTy => "`impl Trait`",
             DesugaringKind::ForLoop => "`for` loop",
             DesugaringKind::WhileLoop => "`while` loop",
-            DesugaringKind::Replace => "drop and replace",
         }
     }
 }