core: Fix AbstractClientStream Javadoc

Subclasses also need to implement setAuthority(String) and getAttributes() which
come in from the ClientStream interface.

Author: MariusVolkhart

core/src/main/java/io/grpc/internal/AbstractClientStream.java

@@ -43,9 +43,9 @@
 import javax.annotation.Nullable;
 
 /**
- * The abstract base class for {@link ClientStream} implementations. Extending classes only need to
- * implement {@link #transportState()} and {@link #abstractClientStreamSink()}. Must only be called
- * from the sending application thread.
+ * The abstract base class for {@link ClientStream} implementations.
+ *
+ * <p>Must only be called from the sending application thread.
  */
 public abstract class AbstractClientStream extends AbstractStream
     implements ClientStream, MessageFramer.Sink {