Update rdoc to version 6.5
Version 6.5 of rdoc adds official testing pipelines for Ruby 3.1 and 3.2, it would be smart to update to this version to ensure our rdoc version is compatible with the latest Ruby.
Note that we have a monkey patch in place for rdoc at config/initializers/rdoc_segfault_patch.rb
, that is related to this issue: https://gitlab.com/gitlab-org/gitlab/-/issues/351179
Edited by Roy Zwambag