Merge branch '3.1'

* 3.1:
  `@throws` annotations should go after `@return`
  Fix merge
  updated VERSION for 2.3.42
  update CONTRIBUTORS for 2.3.42
  updated CHANGELOG for 2.3.42
  Revert "bug #18908 [DependencyInjection] force enabling the external XML entity loaders (xabbuh)"
  Partial revert of previous PR
  [DependencyInjection] Skip deep reference check for 'service_container'
  Catch \Throwable
  [Serializer] Add missing @throws annotations
  Fix for #18843
  force enabling the external XML entity loaders
  Removed UTC specification with timestamp

Author: nicolas-grekas