Doc: Fix link to install scheduler plugins as gang scheduler for kubeflow plugins

[fg91]

The current link gives 404.

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.98%. Comparing base (ce5eb03) to head (6617d16).
Report is 144 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5522      +/-   ##
==========================================
- Coverage   60.99%   60.98%   -0.01%     
==========================================
  Files         794      794              
  Lines       51475    51475              
==========================================
- Hits        31397    31392       -5     
- Misses      17186    17191       +5     
  Partials     2892     2892              

Flag	Coverage Δ
unittests-datacatalog	69.31% <ø> (ø)
unittests-flyteadmin	58.69% <ø> (-0.05%)	⬇️
unittests-flytecopilot	17.79% <ø> (ø)
unittests-flytectl	68.03% <ø> (ø)
unittests-flyteidl	79.04% <ø> (ø)
unittests-flyteplugins	61.85% <ø> (ø)
unittests-flytepropeller	57.30% <ø> (ø)
unittests-flytestdlib	65.59% <ø> (+0.02%)	⬆️

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[neverett]

Looks like this was fixed in #5524 -- sorry, I didn't see this earlier PR!