Fix proguard from stripping inner plugin classes

Test: Class is still present
Change-Id: I92cfaf38d4a9ff653033c141ce9edc49c63fcf25
diff --git a/packages/SystemUI/proguard.flags b/packages/SystemUI/proguard.flags
index e6452e7..fa4c8b5 100644
--- a/packages/SystemUI/proguard.flags
+++ b/packages/SystemUI/proguard.flags
@@ -39,6 +39,6 @@
 -keep class ** extends androidx.preference.PreferenceFragment
 -keep class com.android.systemui.tuner.*
 -keep class com.android.systemui.plugins.** {
-    public protected *;
+    *;
 }
 -keep class androidx.core.app.CoreComponentFactory