fix link check badge in README

[stephprince]

Motivation

The link checker badge is currently broken in the README, because it points to an old workflow name.

How to test the behavior?

View updated README.

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.96%. Comparing base (8d9aaa3) to head (11e9b55).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1871   +/-   ##
=======================================
  Coverage   91.96%   91.96%           
=======================================
  Files          27       27           
  Lines        2663     2663           
  Branches      686      686           
=======================================
  Hits         2449     2449           
  Misses        142      142           
  Partials       72       72           

Flag	Coverage Δ
integration	72.36% <ø> (ø)
unit	84.07% <ø> (ø)

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