docs: use the CL anthology link for the SIGUL paper

[joanise]

The ACL anthology links are much nicer to share.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.05%. Comparing base (8d8dfc2) to head (e036bd9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #207   +/-   ##
=======================================
  Coverage   87.05%   87.05%           
=======================================
  Files          21       21           
  Lines        1746     1746           
  Branches      315      315           
=======================================
  Hits         1520     1520           
  Misses        189      189           
  Partials       37       37           

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[github-actions]

CLI load time: 0:00.34
Pull Request HEAD: e036bd922b9c946cc1078e83a148fa794d6bf14f
Imports that take more than 0.1 s:
import time: self [us] | cumulative | imported package
import time:    246389 |     304739 | pkg_resources

[dhdaines]

agreed!