Remove dead helper methods from Block AST node

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 81545cd72af03ac530ad1be0523ef2eb01c19891..af6ecb8d10647d27faf9d01f5dc37928b30b77aa 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -458,14 +458,6 @@ class Block final : public BreakableStatement {
  public:
   DECLARE_NODE_TYPE(Block)
 
-  void AddStatement(Statement* statement, Zone* zone) {
-    statements_.Add(statement, zone);
-  }
-
-  void InsertStatementAt(int index, Statement* statement, Zone* zone) {
-    statements_.InsertAt(index, statement, zone);
-  }
-
   ZoneList<Statement*>* statements() { return &statements_; }
   bool ignore_completion_value() const { return ignore_completion_value_; }