Use 'authored_date' instead of 'committed_date' for simple tags
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=19848)
</details>
<!--IssueSummary end-->
Annotated tags have a created date, but simple tags do not. We correctly use the created date for annotated tags, but the committed date is misleading for annotated tags.
### Proposal
Use `authored_date` for simple tags
### Original report
Zendesk ticket: https://gitlab.zendesk.com/agent/tickets/83757
A customer is saying that the `authored_date` on a tag currently shows when the commit the tag points to was created, instead of when the tag itself was authored.
>I'd like to submit a bug saying that this could be explained more explicitly, since an annotated tag will contain a lot of the same data (author name, date, and so on) a commit would.
>At the same time, I'd also like to request a feature for GitLab to let me get the creation date of tags which has this information (like annotated tags).
>My sincere apologies for the ambiguity! =)
>(But I would submit that it's easy for human eyes to glass over the fact that 'authored_date' is inside the 'commit' JSON dict/map when reading your example on the link I provided).
He linked here: https://docs.gitlab.com/ee/api/tags.html
/cc @jramsay
issue