doc(tutorials): Correct card of the "Custom operators" tutorial

[luisaFelixSalles]

This PR corrects how the card of the "Custom operators" tutorial renders on the "Custom Operators and Plugins" tutorial section
Before:

After:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.15%. Comparing base (cf099e4) to head (f754753).
⚠️ Report is 4 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2494      +/-   ##
==========================================
- Coverage   84.19%   84.15%   -0.05%     
==========================================
  Files          91       91              
  Lines       10683    10683              
==========================================
- Hits         8995     8990       -5     
- Misses       1688     1693       +5