android_jni: Update proguard rules to keep AvifDecoder/*

JNI accesses variables in this class. So they have to be kept
unobfuscated.

GOOGLE_INTERNAL_CL: 524122665
diff --git a/android_jni/avifandroidjni/proguard-rules.pro b/android_jni/avifandroidjni/proguard-rules.pro
index 0a7ce37..180acda 100644
--- a/android_jni/avifandroidjni/proguard-rules.pro
+++ b/android_jni/avifandroidjni/proguard-rules.pro
@@ -7,8 +7,11 @@
   native <methods>;
 }
 
-# Members of this class may be accessed from native methods. Keep them
+# Members of these classes may be accessed from native methods. Keep them
 # unobfuscated.
+-keep class org.aomedia.avif.android.AvifDecoder {
+  *;
+}
 -keep class org.aomedia.avif.android.AvifDecoder$Info {
   *;
 }