fix: lockscreen slider targets custom icon FC on Gallery.

-Error indicated that there was not intent receiver for
com.slim.ACTION_PICK_ICON. Changed intent to android.intent.action.PICK.

-Causes "Icon Pack" to appear which did not do anything for me but
did not cause an error either

Change-Id: I735d7b9a8e327684f5e70077fc138fe431dd430c