mediav2 CTS: Release codec resource after test

Media resource is held up after mCodec.reset() without releasing explicitly.

Bug: 207744112
Test: android.mediav2.cts.AdaptivePlaybackTest
Change-Id: Ibf7ca418366291f16e2dddf53fdd7831b198349b
diff --git a/tests/media/src/android/mediav2/cts/AdaptivePlaybackTest.java b/tests/media/src/android/mediav2/cts/AdaptivePlaybackTest.java
index e803863..ae9054f 100644
--- a/tests/media/src/android/mediav2/cts/AdaptivePlaybackTest.java
+++ b/tests/media/src/android/mediav2/cts/AdaptivePlaybackTest.java
@@ -219,6 +219,7 @@
             queueEOS();
             waitForAllOutputs();
             mCodec.reset();
+            mCodec.release();
         }
         tearDownSurface();
     }