Docs: Fix code highlighting in third-party libraries integration guide

[AdrianoKF]

After a refactoring of the transactions feature, the code examples themselves were modied, but not the page that highlights some lines in them.

This PR updates those code blocks to make them consistent with the actual example code.

Additionally, it pins the Python version used for pre-commit hooks to 3.11, to prevent problems on systems with Python 3.12 (which would be used to lock dependencies using pip-compile, which includes the Python version number in a comment in the generated dependency lock file).

Closes #267

[codecov[bot]]

Codecov Report

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

Project coverage is 94.32%. Comparing base (bad9dd8) to head (4d07d8a).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #268 +/- ## ======================================= Coverage 94.32% 94.32% ======================================= Files 5 5 Lines 388 388 Branches 72 72 ======================================= Hits 366 366 Misses 13 13 Partials 9 9 ```

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