Remove deprecated free() calls (#1925)

Replaced with the standard close()

wpilibj/src/main/java/edu/wpi/first/wpilibj/RobotBase.java

@@ -105,10 +105,6 @@ public abstract class RobotBase implements AutoCloseable {
     return m_threadId;
   }
 
-  @Deprecated
-  public void free() {
-  }
-
   @Override
   public void close() {
   }