Don't include NUL byte in _NET_WM_NAME (#658)

> The contents of the property are not required to be null-terminated;
> any terminating null should not be included in text_prop.nitems.

https://tronche.com/gui/x/xlib/ICC/client-to-window-manager/XmbTextPropertyToTextList.html

src/platform/linux/x11/window.rs

@@ -600,7 +600,7 @@ impl UnownedWindow {
                 wm_name_atom,
                 utf8_atom,
                 util::PropMode::Replace,
-                title.as_bytes_with_nul(),
+                title.as_bytes(),
             )
         }
     }