Update snapshot for chapter 12

nostarch/chapter12.md

@@ -1,3 +1,8 @@
+<!-- DO NOT EDIT THIS FILE.
+
+This file is periodically generated from the content in the `/src/`
+directory, so all fixes need to be made in `/src/`.
+-->
 
 [TOC]
 
@@ -37,6 +42,7 @@ Our `grep` project will combine a number of concepts you’ve learned so far:
 * Handling errors (Chapter 9)
 * Using traits and lifetimes where appropriate (Chapter 10)
 * Writing tests (Chapter 11)
+
 We’ll also briefly introduce closures, iterators, and trait objects, which
 Chapters 13 and 17 will cover in detail.
 
@@ -347,6 +353,7 @@ should be limited to the following:
 * Setting up any other configuration
 * Calling a `run` function in *lib.rs*
 * Handling the error if `run` returns an error
+
 This pattern is about separating concerns: *main.rs* handles running the
 program, and *lib.rs* handles all the logic of the task at hand. Because you
 can’t test the `main` function directly, this structure lets you test all of
@@ -1626,7 +1633,6 @@ fn main() {
 
     if let Err(e) = minigrep::run(config) {
         eprintln!("Application error: {e}");
-
         process::exit(1);
     }
 }