Fix javadoc for new methods

core/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java

@@ -721,6 +721,7 @@ public abstract class StreamInput extends InputStream {
      * Default implementation throws {@link UnsupportedOperationException} as StreamInput doesn't hold a registry.
      * Use {@link FilterInputStream} instead which wraps a stream and supports a {@link NamedWriteableRegistry} too.
      */
+    @Nullable
     public <C extends NamedWriteable<?>> C readNamedWriteable(@SuppressWarnings("unused") Class<C> categoryClass) throws IOException {
         throw new UnsupportedOperationException("can't read named writeable from StreamInput");
     }

core/src/main/java/org/elasticsearch/common/io/stream/StreamOutput.java

@@ -689,7 +689,7 @@ public abstract class StreamOutput extends OutputStream {
     }
 
     /**
-     * Write an optional {@link QueryBuilder} to the stream.
+     * Write an optional {@link NamedWriteable} to the stream.
      */
     public void writeOptionalNamedWriteable(@Nullable NamedWriteable<?> namedWriteable) throws IOException {
         if (namedWriteable == null) {