xmonad: fix Signal not moving to the chat workspace

Signal 8.x sets its WM_CLASS to lowercase "signal", so the case-sensitive "Signal" rule no longer matched. Merge it with the discord rule into a case-insensitive classIn.

.config/xmonad/xmonad.hs

@@ -380,7 +380,7 @@ myManageHook =
       title =? "Genshin Impact" --> doShift wsGames,
       classIn ["gimp", "audacity"] --> doShift wsMedia,
       classIn ["pavucontrol", "org.pulseaudio.pavucontrol", "zenity", "org.gnome.zenity", "lxappearance", "qt5ct", "qt6ct"] --> doFloat,
-      className =? "Signal" --> doShift wsChat,
+      classIn ["signal", "discord"] --> doShift wsChat,
       className =? "Spotify" --> doShift wsMedia,
       className =? "Transmission-gtk" --> doShift wsWeb,
       className =? "Viewnior" --> doFloat,
@@ -388,7 +388,6 @@ myManageHook =
       className =? "Xmessage" --> doFloat,
       className =? "Xreader" --> doShift wsDocs,
       className =? "calibre" --> doShift wsDocs,
-      className =? "discord" --> doShift wsChat,
       className =? "feh" --> doFloat,
       title =? "glxgears" --> doFloat,
       className =? "library_manager" --> doShift wsDocs,