misc/ruby-sprockets-rails: update to 3.2.2

Update ruby-sprockets-rails package to 3.2.2.

3.2.2 (2020-09-12)

* Fix extending ActionView::Base instances with Sprockets::Rails::Helper on
  Rails 6.1
* Fix deprecation warning on Ruby 2.7 [#454]
* action_view/base is no longer required when rake tasks are loaded [#455]
* Asset not precompiled error exception renamed to AssetNotPrecompiledError
  [#414]

(taca)