Upgrade IMA SDK dependency to 3.20.1

This brings in a fix for companion ads rendering when targeting API 29.

Issue: #6432
PiperOrigin-RevId: 337279054

RELEASENOTES.md

@@ -67,6 +67,9 @@
         ([#7961)(https://github.com/google/ExoPlayer/issues/7961)).
     *   Fix truncating large cue points in microseconds
         ([#8067](https://github.com/google/ExoPlayer/issues/8067)).
+    *   Upgrade IMA SDK dependency to 3.20.1. This brings in a fix for
+        companion ads rendering when targeting API 29
+        ([#6432](https://github.com/google/ExoPlayer/issues/6432)).
 
 ### 2.12.0 (2020-09-11) ###
 

extensions/ima/build.gradle

@@ -25,7 +25,7 @@ android {
 }
 
 dependencies {
-    api 'com.google.ads.interactivemedia.v3:interactivemedia:3.19.4'
+    api 'com.google.ads.interactivemedia.v3:interactivemedia:3.20.1'
     implementation project(modulePrefix + 'library-core')
     implementation 'androidx.annotation:annotation:' + androidxAnnotationVersion
     implementation 'com.google.android.gms:play-services-ads-identifier:17.0.0'