GET Issue REST API documentation to be updated

Issue Summary

The documentation for GET Issue endpoint is incorrect.

This issue has been moved from here (check for more details): https://ecosystem.atlassian.net/browse/ACJIRA-2565

Steps to Reproduce

Go to: https://developer.atlassian.com/cloud/jira/platform/rest/v2/api-group-issues/#api-rest-api-2-issue-issueidorkey-get

See that on the response example there is an outdated field called "sub-tasks".

Actual Results

As above

Expected Results

There is a "subtasks" array field containing information similar to the issue response type.

Workaround

None