Some markdown headers needed tweaking to adhere
to standards, including blank lines above and below,
only one space after hash, first header should be
h1, and only one h1 per doc

Signed-off-by: Rémy Coutable <remy@rymai.me>

See https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/6069

Remove unneeded trailing whitespace in lines in
/development /ci /api and /administration docs.

Updating redirected links in the development, install, policy
raketasks and university dirs. Should now link to final
URL to avoid redirect hops

Fixing square brackets, links, etc in:
  merge_requests.md
  vulnerabilities.md
  issues.md
  issues_statistics.md
  pipelines.md
  services.md
  group_milestones.md
  milestones.md
  runners.md
  changelog.md
  issue_workflow.md
  elasticsearch.md
  api_graphql_styleguide.md
  automatic_ce_ee_merge.md
  file_storage.md
  architecture.md
  database_debugging.md
  index.md
  index.md
  frontend_testing.md
  pry_debugging.md
  vue.md
  development_process.md

After review, heading was changed and links to
it needed to be updated, and minor tweaks to
the issues docs such as note formatting