workspace: Allow full-sized window previews

Previews are currently limited to at most 70% of the actual window
size. This was done to indicate more clearly that the overview is
active and the window cannot be interacted with. However since then
other indications like the vignette effect have been added, so
artificially limiting the preview size doesn't look necessary anymore.

https://bugzilla.gnome.org/show_bug.cgi?id=783953

js/ui/workspace.js

@@ -20,7 +20,7 @@ const WindowManager = imports.ui.windowManager;
 
 var WINDOW_DND_SIZE = 256;
 
-var WINDOW_CLONE_MAXIMUM_SCALE = 0.7;
+var WINDOW_CLONE_MAXIMUM_SCALE = 1.0;
 
 var CLOSE_BUTTON_FADE_TIME = 0.1;