Update javadoc as instructed in b/184654824.

Bug: 184654824
Test: Javadoc

Change-Id: I6817f683f8945f26f8539645c8c92302f82e7348

media/java/android/media/musicrecognition/RecognitionRequest.java

@@ -120,7 +120,10 @@ public final class RecognitionRequest implements Parcelable {
             return this;
         }
 
-        /** Number of samples to drop from the start of the stream. */
+        /**
+         * Number of frames to drop from the start of the stream
+         * (if recording is PCM stereo, one frame is two samples).
+         **/
         @NonNull
         public Builder setIgnoreBeginningFrames(int ignoreBeginningFrames) {
             mIgnoreBeginningFrames = ignoreBeginningFrames;