Remove the usage of deprecated function.

mv.pm.night_mode() is deprecated (see
1ed2cce648/qt/aqt/profiles.py (L537)).
Furthermore, on anki Version ⁨2.1.54, Python 3.9.10 Qt 6.3.1 PyQt 6.3.1, this function returns false, even when the dark mode is set.

src/__init__.py

@@ -82,10 +82,7 @@ class EditorPreview(object):
         c = note.ephemeral_card()
         a = mw.prepare_card_text_for_display(c.answer())
         a = gui_hooks.card_will_show(a, c, "clayoutAnswer")
-        if theme_manager.night_mode:
-            bodyclass = theme_manager.body_classes_for_card_ord(c.ord, mw.pm.night_mode())
-        else:
-            bodyclass = theme_manager.body_classes_for_card_ord(c.ord)
+        bodyclass = theme_manager.body_classes_for_card_ord(c.ord, theme_manager.night_mode)
         bodyclass += " editor-preview"
 
         return f"_showAnswer({json.dumps(a)},'{bodyclass}');"