docs(web): suppress a warning reported by sphinx

[codecov[bot]]

Codecov Report

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

Comparison is base (96f9a1c) 85.37% compared to head (05cc67b) 85.37%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3933 +/- ## ======================================= Coverage 85.37% 85.37% ======================================= Files 234 234 Lines 56199 56199 ======================================= Hits 47980 47980 Misses 8219 8219 ```

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