Update git submodules
- Update extensions/ArticlePlaceholder from branch 'wmf/1.33.0-wmf.13' to rEARP9e19c13db07d
- Pass a usageAccumulator to SidebarGenerator
Bug: T213739 Change-Id: I6d776985135520daa8e6c1a8b09c2381d95aa177
- Pass a usageAccumulator to SidebarGenerator