Allow deleting comments via API

Zendesk issue: https://gitlab.zendesk.com/agent/tickets/14629

Customer would like the ability to delete comments on a merge request/issue. Currently we support adding comments or getting exist comments.

It shouldn't be too much work to expose this via the API.

cc/ @JobV

Makes a lot of sense.

Milestone changed to 8.6

Milestone changed to 8.7

Reassigned to @zj

mentioned in merge request !3557 (merged)

Did not see this issue until I created the MR. @zj I hope you don't mind.

@razer6 Not at all!

mentioned in issue #14986 (closed)

Assignee removed

Reassigned to @razer6

Status changed to closed by commit e322b993

mentioned in commit e322b993

mentioned in issue #30382 (closed)