Remove navigation up button from full preview page

 - Remove navigation up button since it only used by the old layout and
 undownloaded live wallpaper preview page, we already implement the new
 layout/design

 Fixes: 156591242
 Test: manually

Change-Id: I5c59ef936e1e8474031405ca71bc2aa56141bea6
diff --git a/src/com/android/wallpaper/picker/PreviewFragment.java b/src/com/android/wallpaper/picker/PreviewFragment.java
index 242d650..eb26df0 100755
--- a/src/com/android/wallpaper/picker/PreviewFragment.java
+++ b/src/com/android/wallpaper/picker/PreviewFragment.java
@@ -197,10 +197,7 @@
 
         AppCompatActivity activity = (AppCompatActivity) requireActivity();
         activity.setSupportActionBar(toolbar);
-        activity.getSupportActionBar().setDisplayHomeAsUpEnabled(true);
         activity.getSupportActionBar().setDisplayShowTitleEnabled(false);
-        toolbar.getNavigationIcon().setTint(getAttrColor(activity, android.R.attr.colorPrimary));
-        toolbar.getNavigationIcon().setAutoMirrored(true);
 
         mLoadingProgressBar = view.findViewById(getLoadingIndicatorResId());
         mLoadingProgressBar.show();