xwayland: Clear ConstrainCursorHarder in xwl_screen_init_output

In the rootless case, Xwayland receives pointer motion events only while
the pointer is over one of its Wayland surfaces, so there's no need for
constraining them to RandR boundaries.

This also avoids them getting spuriously constrained when using RandR
emulation for modes larger than the default one.

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2095>

hw/xwayland/xwayland-output.c

@@ -1189,6 +1189,8 @@ xwl_screen_init_output(struct xwl_screen *xwl_screen)
     if (!RRScreenInit(xwl_screen->screen))
         return FALSE;
 
+    xwl_screen->screen->ConstrainCursorHarder = NULL;
+
     RRScreenSetSizeRange(xwl_screen->screen, 16, 16, 32767, 32767);
 
     rp = rrGetScrPriv(xwl_screen->screen);