Delete transitional method EncodedImage.maybeRetain

Bug: webrtc:9378
Change-Id: Ibe3d5bad835d1725faa38f8e2a804efc9272776e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/155661
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30072}

sdk/android/tests/src/org/webrtc/AndroidVideoDecoderTest.java

@@ -185,7 +185,7 @@ public class AndroidVideoDecoderTest {
 
   private EncodedImage createTestEncodedImage() {
     return EncodedImage.builder()
-        .setBuffer(ByteBuffer.wrap(ENCODED_TEST_DATA))
+        .setBuffer(ByteBuffer.wrap(ENCODED_TEST_DATA), null)
         .setFrameType(FrameType.VideoFrameKey)
         .setCompleteFrame(true)
         .createEncodedImage();