[Rubocop]Follow up on details linter

Description of the proposal

• Fast follow, update details linter to handle desc blocks that only contain detail
• The purpose of linting this param attribute is for the purposes of improving out OpenAPI documentation
• it is helpful for our api definitions to be consistent and param descriptions benefit api users

#578001

How to Validate these changes

Running the linter

1. Open any grape entity file and update so one of the desc blocks only contains detail
2. Run the linter on that file ie rubocop --only API/DescriptionDetail lib/api/badges.rb
3. Observe no offense that was added

Check-list

• Make sure this MR enables a static analysis check rule for new usage but ignores current offenses.
• Mention this proposal in the relevant Slack channels (e.g. #development, #backend, #frontend).
• If there is a choice to make between two potential styles, set up an emoji vote in the MR:
  • CHOICE_A: 🅰️
  • CHOICE_B: 🅱️
  • Vote for both choices, so they are visible to others.
• The MR doesn't have significant objections, and is getting a majority of 👍 vs 👎 (remember that we don't need to reach a consensus).
• (If applicable) One style is getting a majority of vote (compared to the other choice).
• (If applicable) Update the MR with the chosen style.
• Create a follow-up issue to fix the current offenses as a separate iteration: ISSUE_LINK
• Follow the review process as usual.
• Once approved and merged by a maintainer, mention it again:
  • In the relevant Slack channels (e.g. #development, #backend, #frontend).
  • (Optional depending on the impact of the change) In the Engineering Week in Review.