This helps The Finals which stopped working after recent game update.
The todo is test is related to https://gitlab.winehq.org/wine/wine/-/merge_requests/283 . That MR is otherwise orhtogonal though, it relates to sanitizing flags in the context passed to NtContextThread, whlie this one concerns what happens when NT flag is set by app upon calling syscall.
It could maybe look reasonable to sanitize the flag on syscall entry, but then the test shows that returned r11 value and the flags (apart from NtSetContextThread) keep NT flag, so fixing up before iret avoids some complication and also avoids adding extra to default syscall path.