ui: Mark a string translatable

- Mark the "Special thanks to" string translatable.

src/main.py

@@ -230,7 +230,7 @@ class ImaginerApplication(Adw.Application):
             except KeyError:  # provider not in data
                 pass
 
-    def on_about_action(self, widget, _):
+    def on_about_action(self, widget, *args):
         """Callback for the app.about action."""
         about = Adw.AboutWindow(
             transient_for=self.props.active_window,
@@ -260,7 +260,7 @@ class ImaginerApplication(Adw.Application):
         )
 
         about.add_acknowledgement_section(
-            "Special thanks to",
+            _("Special thanks to"),
             [
                 "Telegraph https://apps.gnome.org/app/io.github.fkinoshita.Telegraph",
                 "Apostrophe https://apps.gnome.org/app/org.gnome.gitlab.somas.Apostrophe",