Auto merge of #23522 - steveklabnik:gh22518, r=Manishearth

When investigating #22518, this chapter is really the only part that has `rand`, and the rest still works without it. We should have some examples like this, but for now, it's more important to be right than perfect.

Author: bors

src/doc/trpl/SUMMARY.md

@@ -14,7 +14,6 @@
     * [Strings](strings.md)
     * [Arrays, Vectors, and Slices](arrays-vectors-and-slices.md)
     * [Standard Input](standard-input.md)
-    * [Guessing Game](guessing-game.md)
 * [II: Intermediate Rust](intermediate.md)
     * [Crates and Modules](crates-and-modules.md)
     * [Testing](testing.md)