common: Bump copyright year

Author: tchx84

src/gameeky/common/widgets/about_window.ui

@@ -6,7 +6,7 @@
   <object class="AdwAboutWindow" id="AboutWindow">
     <property name="application-icon">dev.tchx84.Gameeky</property>
     <property name="application-name">Gameeky</property>
-    <property name="copyright">© 2023-2025 Martín Abente Lahaye</property>
+    <property name="copyright">© 2023-2026 Martín Abente Lahaye</property>
     <property name="designers">Jakub Steiner
 Tobias Bernard</property>
     <property name="developer-name">Martín Abente Lahaye</property>