Fix slight Markdown mishap in chapter 7

book/src/chapter_7.md

@@ -149,7 +149,7 @@ Now we'll make a new component, `BlocksTile`. You should know the drill by now;
 ```rust
 #[derive(Component, Debug)]
 pub struct BlocksTile {}
-```rust
+```
 
 Then register it in `main.rs`: `gs.ecs.register::<BlocksTile>();`
 
@@ -759,4 +759,4 @@ That was quite the chapter! We added in location indexing, damage, and killing t
 
 Copyright (C) 2019, Herbert Wolverson.
 
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+---