Correct Node's clipping rectangle

Fixing the Node's clipping rectangle make the clipping in DocView:draw()
partially redundant. This latter is now no longer needed to clip
on the right when drawing the document's lines but it still serves to
the purpose of clipping on the left, before the gutter region.

data/core/rootview.lua

@@ -595,7 +595,7 @@ function Node:draw()
       self:draw_tabs()
     end
     local pos, size = self.active_view.position, self.active_view.size
-    core.push_clip_rect(pos.x, pos.y, pos.x + size.x, pos.y + size.y)
+    core.push_clip_rect(pos.x, pos.y, size.x, size.y)
     self.active_view:draw()
     core.pop_clip_rect()
   else