Fix CMenuManager::DrawQuitGameScreen signature

[Akionka]

Removes the incorrect int unused parameter from CMenuManager::DrawQuitGameScreen.

The function at 0x57D860 in GTA SA 1.0 US uses ECX as this and ends with a plain:

ret

rather than:

ret 4

For an x86 __thiscall function, a single explicit 32-bit argument would be passed on the stack and cleaned up by the callee with ret 4, even if the argument itself was unused.

Therefore the function appears to have no explicit parameters.

Changed from:

void CMenuManager::DrawQuitGameScreen(int unused) {
    plugin::CallMethod<0x57D860, CMenuManager*>(this, unused);
}

to:

void CMenuManager::DrawQuitGameScreen() {
    plugin::CallMethod<0x57D860, CMenuManager*>(this);
}

This also avoids the stack/calling-convention mismatch caused by passing an argument to a function that does not clean it up.