fix: correct into_iter() example to compile properly (#1904)

The into_iter() example previously used `println!("names: {:?}", names)`
after the collection was consumed, causing a compilation error. Commented
out the offending line with an explanation and removed the `ignore` flag
so the example is now compilable and runnable.

Author: Abhinav-ranish

src/flow_control/for.md

@@ -80,7 +80,7 @@ fn main() {
   data is provided. Once the collection has been consumed it is no longer
   available for reuse as it has been 'moved' within the loop.
 
-```rust,editable,ignore,mdbook-runnable
+```rust,editable
 fn main() {
     let names = vec!["Bob", "Frank", "Ferris"];
 
@@ -91,8 +91,9 @@ fn main() {
         }
     }
 
-    println!("names: {:?}", names);
-    // FIXME ^ Comment out this line
+    // `names` has been 'moved' and can no longer be used.
+    // Try uncommenting the line below to see the compiler error:
+    // println!("names: {:?}", names);
 }
 ```