Update request_body.md

[vituri]

fix example with dict in the docs

[codecov[bot]]

Codecov Report

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

Project coverage is 99.33%. Comparing base (a212dfe) to head (cc7693d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #176 +/- ## ======================================= Coverage 99.33% 99.33% ======================================= Files 23 23 Lines 1198 1198 ======================================= Hits 1190 1190 Misses 8 8 ```

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