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

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

diff --cc src/doc/trpl/SUMMARY.md
index 0edadeb628e8036bd6ead12e71797406af7f01a8,b0ee8e1fa930899cf51d64d85c3bc13d8d74a99e..7ce74e86fef63450f2cd002d2aecec07a7dcd7eb
--- 1/src/doc/trpl/SUMMARY.md
--- 2/src/doc/trpl/SUMMARY.md
+++ b/src/doc/trpl/SUMMARY.md
@@@ -7,9 -7,7 +7,8 @@@
  * [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)
      * [Iterators](iterators.md)
      * [Concurrency](concurrency.md)