Use recently stabilized intra-doc links

See RFC: https://github.com/rust-lang/rfcs/blob/master/text/1946-intra-rustdoc-links.md

graphics/src/widget/pane_grid.rs

@@ -7,7 +7,6 @@
 //! drag and drop, and hotkey support.
 //!
 //! [`pane_grid` example]: https://github.com/hecrj/iced/tree/0.1/examples/pane_grid
-//! [`PaneGrid`]: type.PaneGrid.html
 use crate::backend::{self, Backend};
 use crate::defaults;
 use crate::{Primitive, Renderer};