gradle: update leanback

Change-Id: I78202e52bde151c0d040ec193cbc1165537cce21
diff --git a/ring-android/app/build.gradle b/ring-android/app/build.gradle
index a6e70a2..cae88ff 100644
--- a/ring-android/app/build.gradle
+++ b/ring-android/app/build.gradle
@@ -83,8 +83,8 @@
     implementation "androidx.cardview:cardview:$android_support_version"
     implementation "androidx.preference:preference:$android_support_core_version"
     implementation "androidx.recyclerview:recyclerview:$android_support_core_version"
-    implementation "androidx.leanback:leanback:1.1.0-alpha02"
-    implementation "androidx.leanback:leanback-preference:1.1.0-alpha02"
+    implementation "androidx.leanback:leanback:1.1.0-alpha03"
+    implementation "androidx.leanback:leanback-preference:1.1.0-alpha03"
     implementation "androidx.media:media:$android_support_core_version"
     implementation "com.google.android.material:material:$material_version"
     implementation 'com.google.android:flexbox:1.1.1'