Revert "Hack to make binaryen eliminate redundant casts"

This reverts commit 25315fb4d3231ecd0fdc07c57adec59f3e697dc3.

No longer useful with WebAssembly/binaryen#6507

Author: vouillon

compiler/lib/wasm/wa_gc_target.ml

@@ -616,13 +616,7 @@ end
 module Memory = struct
   let wasm_cast ty e =
     let* e = e in
-    match e with
-    | W.LocalGet x ->
-        return
-          (W.RefCast
-             ( { nullable = false; typ = Type ty }
-             , W.LocalTee (x, W.RefCast ({ nullable = false; typ = Type ty }, e)) ))
-    | _ -> return (W.RefCast ({ nullable = false; typ = Type ty }, e))
+    return (W.RefCast ({ nullable = false; typ = Type ty }, e))
 
   let wasm_struct_get ty e i =
     let* e = e in