update some usage of println! to dbg!

src/ch08-03-hash-maps.md

@@ -179,7 +179,7 @@ let mut scores = HashMap::new();
 scores.insert(String::from("Blue"), 10);
 scores.insert(String::from("Blue"), 25);
 
-println!("{:?}", scores);
+dbg!(scores);
 ```
 
 <span class="caption">Listing 8-24: Replacing a value stored with a particular
@@ -208,7 +208,7 @@ scores.insert(String::from("Blue"), 10);
 scores.entry(String::from("Yellow")).or_insert(50);
 scores.entry(String::from("Blue")).or_insert(50);
 
-println!("{:?}", scores);
+dbg!(scores);
 ```
 
 <span class="caption">Listing 8-25: Using the `entry` method to only insert if
@@ -247,7 +247,7 @@ for word in text.split_whitespace() {
     *count += 1;
 }
 
-println!("{:?}", map);
+dbg!(map);
 ```
 
 <span class="caption">Listing 8-26: Counting occurrences of words using a hash

src/ch12-01-accepting-command-line-arguments.md

@@ -45,7 +45,7 @@ use std::env;
 
 fn main() {
     let args: Vec<String> = env::args().collect();
-    println!("{:?}", args);
+    dbg!(args);
 }
 ```
 

src/ch16-03-shared-state.md

@@ -64,7 +64,7 @@ fn main() {
         *num = 6;
     }
 
-    println!("m = {:?}", m);
+    dbg!(m);
 }
 ```
 

src/ch18-03-pattern-syntax.md

@@ -464,7 +464,7 @@ match (setting_value, new_setting_value) {
     }
 }
 
-println!("setting is {:?}", setting_value);
+dbg!(setting_value);
 ```
 
 <span class="caption">Listing 18-18: Using an underscore within patterns that
@@ -538,7 +538,7 @@ if let Some(_s) = s {
     println!("found a string");
 }
 
-println!("{:?}", s);
+dbg!(s);
 ```
 
 <span class="caption">Listing 18-21: An unused variable starting with an
@@ -556,7 +556,7 @@ if let Some(_) = s {
     println!("found a string");
 }
 
-println!("{:?}", s);
+dbg!(s);
 ```
 
 <span class="caption">Listing 18-22: Using an underscore does not bind the