[gnome-calculator/gnome-42] Fixed undo/redo broken (#266)

[Robert Roth <robertroth src gnome org>]

commit 4f0f435d2ff3ca55e545d8fd7dc9c22160a38458
Author: Robert Roth <robert roth off gmail com>
Date:   Fri May 13 08:41:40 2022 +0300

    Fixed undo/redo broken (#266)

 lib/math-equation.vala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/lib/math-equation.vala b/lib/math-equation.vala
index 24bf9218..47427680 100644
--- a/lib/math-equation.vala
+++ b/lib/math-equation.vala
@@ -535,7 +535,7 @@ public class MathEquation : GtkSource.Buffer
             insert (text.delimit ("\n", ' '));
     }
 
-    public override void undo ()
+    public new void undo ()
     {
         if (undo_stack == null)
         {
@@ -556,7 +556,7 @@ public class MathEquation : GtkSource.Buffer
         apply_state (state);
     }
 
-    public override void redo ()
+    public new void redo ()
     {
         if (redo_stack == null)
         {