ci: Fix artifact name for schema web validator deployment

[nellh]

trafficstars

Fix for No artifacts named "github-pages" were found for this workflow run. Ensure artifacts are uploaded with actions/upload-artifact@v4 or later.

https://github.com/bids-standard/bids-validator/actions/runs/9023707172/job/24796100179

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.59%. Comparing base (bce7cc8) to head (ef0021a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1970      +/-   ##
==========================================
+ Coverage   85.68%   88.59%   +2.91%     
==========================================
  Files          91       39      -52     
  Lines        3792     2210    -1582     
  Branches     1220      282     -938     
==========================================
- Hits         3249     1958    -1291     
+ Misses        457      247     -210     
+ Partials       86        5      -81     

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