refactor: make microWacc.ArrayElem recursive rather than flat

src/main/wacc/frontend/microWacc.scala

@@ -1,7 +1,5 @@
 package wacc
 
-import cats.data.NonEmptyList
-
 object microWacc {
   import wacc.types._
 
@@ -19,9 +17,7 @@ object microWacc {
       extends Expr(identTy)
       with CallTarget(identTy)
       with LValue
-  case class ArrayElem(value: LValue, indices: NonEmptyList[Expr])(ty: SemType)
-      extends Expr(ty)
-      with LValue
+  case class ArrayElem(value: LValue, index: Expr)(ty: SemType) extends Expr(ty) with LValue
 
   // Operators
   case class UnaryOp(x: Expr, op: UnaryOperator)(ty: SemType) extends Expr(ty)