[trivial] regression: qt5 failed to build with new libxkbcommon 1.6.0

The new package libxkbcommon removed unused/useless dead key:

(from libxkbcommon-1.6.0/NEWS)
Code:### Breaking changes

- *Remove* keysyms that were intended for German T3 layout but are unused:

- `XKB_KEY_dead_lowline`
- `XKB_KEY_dead_aboveverticalline`
- `XKB_KEY_dead_belowverticalline`
- `XKB_KEY_dead_longsolidusoverlay`

See the upstream [`xorgproto` MR](https://gitlab.freedesktop.org/xorg/proto/xorgproto/-/merge_requ
ests/70). See hereinafter for further changes related to keysyms.But these keysyms were not removed from qt5:
Code:--- qt-everywhere-src-5.15.10_20230923_6e8e373e/qtbase/src/platformsupport/input/xkbcommon/qxkbcommon.cpp.orig 2023-09-24 21:38:04.000000000 +0200
+++ qt-everywhere-src-5.15.10_20230923_6e8e373e/qtbase/src/platformsupport/input/xkbcommon/qxkbcommon.cpp 2023-10-14 10:39:15.063750011 +0200
@@ -274,10 +274,6 @@ static constexpr const auto KeyTbl = qMa
Xkb2Qt<XKB_KEY_dead_small_schwa, Qt::Key_Dead_Small_Schwa>,
Xkb2Qt<XKB_KEY_dead_capital_schwa, Qt::Key_Dead_Capital_Schwa>,
Xkb2Qt<XKB_KEY_dead_greek, Qt::Key_Dead_Greek>,
- Xkb2Qt<XKB_KEY_dead_lowline, Qt::Key_Dead_Lowline>,
- Xkb2Qt<XKB_KEY_dead_aboveverticalline, Qt::Key_Dead_Aboveverticalline>,
- Xkb2Qt<XKB_KEY_dead_belowverticalline, Qt::Key_Dead_Belowverticalline>,
- Xkb2Qt<XKB_KEY_dead_longsolidusoverlay, Qt::Key_Dead_Longsolidusoverlay>,

// Special keys from X.org - This include multimedia keys,
// wireless/bluetooth/uwb keys, special launcher keys, etc.The bug was already fixed in 5.15.16, but not in actual Slackware's version (5.15.10): https://bugreports.qt.io/browse/QTBUG-117950

Since the fix is very trivial, I think we can wait the next qt5 refresh to apply the patch.