Rollup merge of rust-lang#24698 - steveklabnik:remove_debug_display, r=steveklabnik

this is too small for its own thing, I think.

Author: Manishearth

src/doc/trpl/SUMMARY.md

@@ -7,7 +7,6 @@
 * [Learn Rust](learn-rust.md)
 * [Effective Rust](effective-rust.md)
     * [The Stack and the Heap](the-stack-and-the-heap.md)
-    * [Debug and Display](debug-and-display.md)
     * [Testing](testing.md)
     * [Conditional Compilation](conditional-compilation.md)
     * [Documentation](documentation.md)