Grant set wallpaper dim amount permission to Wallpaper Picker (4/5)

Grant permission needed for the new WallpaperManager method
getWallpaperColors, to prepare for enabling color preview in the
multi-crop UI.

Flag: ACONFIG com.android.wallpaper.multi_crop_preview_ui_flag DEVELOPMENT
Bug: 315856338
Test: manually verified
Change-Id: Ied82df73e7f3d3573b01ecf7335824c37cfd2662
diff --git a/data/etc/privapp-permissions-platform.xml b/data/etc/privapp-permissions-platform.xml
index c6f920f..b9efe65 100644
--- a/data/etc/privapp-permissions-platform.xml
+++ b/data/etc/privapp-permissions-platform.xml
@@ -575,6 +575,7 @@
         <permission name="android.permission.SET_WALLPAPER_COMPONENT"/>
         <permission name="android.permission.BIND_WALLPAPER"/>
         <permission name="android.permission.CUSTOMIZE_SYSTEM_UI"/>
+        <permission name="android.permission.SET_WALLPAPER_DIM_AMOUNT"/>
     </privapp-permissions>
 
     <privapp-permissions package="com.android.dynsystem">