Replace link to learn-rust in the book

It was removed in #30595.
Also delete the old learn-rust.md.

Author: ollie27

src/doc/book/getting-started.md

@@ -604,11 +604,11 @@ This chapter covered the basics that will serve you well through the rest of
 this book, and the rest of your time with Rust. Now that you’ve got the tools
 down, we'll cover more about the Rust language itself.
 
-You have two options: Dive into a project with ‘[Learn Rust][learnrust]’, or
+You have two options: Dive into a project with ‘[Tutorial: Guessing Game][guessinggame]’, or
 start from the bottom and work your way up with ‘[Syntax and
 Semantics][syntax]’. More experienced systems programmers will probably prefer
-‘Learn Rust’, while those from dynamic backgrounds may enjoy either. Different
+‘Tutorial: Guessing Game’, while those from dynamic backgrounds may enjoy either. Different
 people learn differently! Choose whatever’s right for you.
 
-[learnrust]: learn-rust.html
+[guessinggame]: guessing-game.html
 [syntax]: syntax-and-semantics.html