Fixes #2616

Description

This patch uses a SAMPLE() in the SPARQL query to list articles with explicit CiTO annotation only once.

I put effort in making the query not use WITH and is relatively easy to port to QLever.

Caveats

Cannot think of any.

Check any of the following which apply:

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
  • I have made corresponding changes to the documentation
• This change requires new dependencies (please list)

Testing

• Go to Recent articles with explicit CiTO-annotation
• Check if articles are listed only once (see screenshot in bug report for duplication)

Checklist

• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have not used code from external sources without attribution
• I have considered accessibility in my implementation
• There are no remaining debug statements (print, console.log, ...)