Update name of bot and feature

Background

Based on https://gitlab.com/gitlab-org/gitlab/-/issues/463628, we've made a decision to use the name GitLab Duo Code Review for this feature. Given that, we should make some updates wherever the feature is visible:

Proposal

  • Quick Action: /duo_code_review
  • Bot: Duo Code Reviewer duo-code-reviewer
Edited by Kai Armstrong