Fix comments in AV1 extension

PiperOrigin-RevId: 273928626

extensions/av1/src/main/java/com/google/android/exoplayer2/ext/av1/Gav1Decoder.java

@@ -165,9 +165,9 @@ import java.nio.ByteBuffer;
   }
 
   /**
-   * Initializes libgav1 decoder.
+   * Initializes a libgav1 decoder.
    *
-   * @param threads Number of threads used by libgav1 decoder.
+   * @param threads Number of threads to be used by a libgav1 decoder.
    * @return The address of the decoder context or {@link #GAV1_ERROR} if there was an error.
    */
   private native long gav1Init(int threads);

extensions/av1/src/main/java/com/google/android/exoplayer2/ext/av1/Libgav1VideoRenderer.java

@@ -39,7 +39,7 @@ import com.google.android.exoplayer2.video.VideoDecoderOutputBufferRenderer;
 import com.google.android.exoplayer2.video.VideoRendererEventListener;
 
 /**
- * Decodes and renders video using the native libgav1 decoder.
+ * Decodes and renders video using libgav1 decoder.
  *
  * <p>This renderer accepts the following messages sent via {@link ExoPlayer#createMessage(Target)}
  * on the playback thread: