Only keep classes from original shared lib for now

- To be expanded later

Bug: 218593309
Test: Build NLRelease and verify unused classes aren't in the apk
Change-Id: I633872fbc786ef35a6ae7e8661190532e19725dd
diff --git a/proguard.flags b/proguard.flags
index a450183..1f5c065 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -54,7 +54,7 @@
 -dontwarn com.android.internal.util.**
 
 ################ Do not optimize recents lib #############
--keep class com.android.systemui.** {
+-keep class com.android.systemui.shared.** {
   *;
 }