docs: fix cbtc example

[codecov[bot]]

Codecov Report

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

Project coverage is 41.35%. Comparing base (5e36181) to head (707668d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1492 +/- ## ======================================= Coverage 41.35% 41.35% ======================================= Files 87 87 Lines 32619 32619 ======================================= Hits 13489 13489 Misses 19130 19130 ```

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