Fix JavaDoc tag (#995)

The isParented method had an incorrect javadoc tag for the return value.

wpilibj/src/main/java/edu/wpi/first/wpilibj/command/Command.java

@@ -381,7 +381,7 @@ public abstract class Command extends SendableBase implements Sendable {
   /**
    * Returns whether the command has a parent.
    *
-   * @param True if the command has a parent.
+   * @return true if the command has a parent.
    */
   synchronized boolean isParented() {
     return m_parent != null;