Reg[Qt 5.15.4->Qt5.15.5] Qt::MetaModifier and Qt::GroupSwitchModifier is always set

On Linux only, it seems that the QKeyEvent always has the Qt::MetaModifier and Qt::GroupSwitchModifier flags set in the modifiers, even when the keys are not pressed down.

This can be easily reproduce with /examples/widgets/widgets/codeeditor/
Simply typing alphabet characters in this application works. However, the non-
printing characters do not work, like Enter, Backspace, Home, End, and cursor

This works with Qt5.15.4 but not with 5.15.5
Reverting patch of QTBUG-49771 fixes it.
keys.