Update 01_Comparable.md

Author: maskleo

ch03/01_Comparable.md

@@ -125,9 +125,9 @@ x.compareTo（x）== 0
 class Integer implements Comparable<Integer> {
   ...
   public int compareTo(Integer that) {
-  return this.value < that.value ? -1 :
-  this.value == that.value ? 0 : 1 ;
-}
+    return this.value < that.value ? -1 :
+    this.value == that.value ? 0 : 1 ;
+  }
 ...
 }
 ```