fix links for linkcheck

[sappelhoff]

• closes circleci: sphinx linkcheck keeps failing "too many requests" #1392

locally, this works now. I still don't know what the issue was for larsoner, marakw, and matthiasdold. Those links do actually exist 🤷

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.49%. Comparing base (260708a) to head (c8e9d00).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1396   +/-   ##
=======================================
  Coverage   97.49%   97.49%           
=======================================
  Files          40       40           
  Lines        9060     9060           
=======================================
  Hits         8833     8833           
  Misses        227      227           

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