Docs: fix failing make

[Borda]

What does this PR do?

a hotfix on failing to make docs... sphinx-doc/sphinx#8880

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[codecov]

Codecov Report

Merging #5988 (25b7fad) into master (d422ef2) will decrease coverage by 0%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #5988   +/-   ##
======================================
- Coverage      90%     90%   -0%     
======================================
  Files         170     170           
  Lines       11789   11789           
======================================
- Hits        10669   10640   -29     
- Misses       1120    1149   +29