fixed small JavaDoc typo

GameProject/src/playground/package-info.java

@@ -2,7 +2,7 @@
  * The package playground contains all level specific logic and control of level logic.
  * The structure and general logic (with global and local flags to be stored/used) 
  * is provided in abstract base class {@link Playground}.<br>
- * Child-classes implement specific logic for one level and game type (e.g. {@link SpaceInvadersLevel}).<b>
+ * Child-classes implement specific logic for one level and game type (e.g. {@link SpaceInvadersLevel}).<br>
  * 
  * Generally, the base class {@link Playground} supports totally different game types to be implemented.
  */