facets: incorrect counts in Author facet

[PascalRepond]

Bug description:

On a document search result page (public or pro UI), the occurence count in the facet is less and less accurate the lower you go in the list. The error margin can go up to 30%.

Example

Expected behavior:

The count should be more accurate, if possible.

Steps to Reproduce:

1. Go to https://sonar.ch/global/search/documents?q=*&page=1&size=10&sort=relevance
2. See that "Zhu J" (last entry in the author facet) should have 304 documents.
   
3. But if you click on this author, there are actually 381 documents.
   

Version:

v1.10.0