Remove x20 dependency on already removed youtube version

Originally removed here https://r8-review.googlesource.com/c/r8/+/64200

Change-Id: I5667a2a86668a1910633c2281d477ed59924853f

build.gradle

diff --git a/build.gradle b/build.gradle
index 532320f..d31a8de 100644
--- a/build.gradle
+++ b/build.gradle
@@ -477,7 +477,6 @@
         "protobuf-lite",
         "retrace_internal",
         "youtube/youtube.android_15.33",
-        "youtube/youtube.android_16.12",
         "youtube/youtube.android_16.20"
     ],
 ]