Fix broken link in javadoc.

        <!-- Sets whether or not this ViewGroup should be treated as a single entity

             when doing an Activity transition. Typically, the elements inside a

             ViewGroup are each transitioned from the scene individually. The default

             for a ViewGroup is false unless it has a background.

             See {@link android.app.ActivityOptions#makeSceneTransitionAnimation(android.os.Bundle)}

             for a ViewGroup is false unless it has a background. See

             {@link android.app.ActivityOptions#makeSceneTransitionAnimation(android.view.View, String)}

             for more information. -->

        <attr name="transitionGroup" format="boolean" />

    </declare-styleable>