Fix or remove broken gitlab/issues and gitlab/epics shortcodes
The `gitlab/issues` and `gitlab/epics` shortcodes are broken due to Hugo deprecation. We need to decide whether to fix them or remove them from the codebase.
**Problem**
The `gitlab/issues` and `gitlab/epics` shortcodes rely on `data.GetJSON`, which was deprecated in Hugo v0.123.0 and subsequently removed. When attempting to use these shortcodes, the following error occurs:
```
ERROR deprecated: data.GetJSON was deprecated in Hugo v0.123.0 and subsequently removed. use resources.Get or resources.GetRemote with transform.Unmarshal
```
**Current Status**
- These shortcodes appear to be unused across the codebase
- No usage found in `gitlab/issues` or `gitlab/epics` shortcodes in downstream projects
**Decision Needed**
We need to determine whether to:
1. **Fix the implementation** by migrating from `data.GetJSON` to `resources.GetRemote` with `transform.Unmarshal`
2. **Remove the shortcodes** if they are confirmed to be unused and no longer needed
**Related**
- Merge request: !292
- Discussion: https://gitlab.com/gitlab-com/content-sites/docsy-gitlab/-/merge_requests/292#note_2877954800
issue