Fixing re-ordering of an issue when dragging it to the bottom a long issue list in the board

What does this MR do?

Fixes a problem that occurs when dragging an issue on the board to the bottom of a list with a text ("Showing all issue"). The text wasn't properly filtered from the sortable and thus recognized as an 'issue' with a garbage ID.

Are there points in the code the reviewer needs to double check?

I changed data-id to data-issue-id, believing that data-id was an error to begin with. Nevertheless, it could also be that the data-id property is used somewhere. Should both be present, or is it ok to remove data-id?

Why was this MR needed?

See #36906 (closed).

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together (will be squashed when MR is accepted)
• Internationalization required/considered

What are the relevant issue numbers?

#36906 (closed)