Fix typo in code sample

[Pankraty]

Code sample from the documentation has a typo making it uncompilable.

[CLAassistant]

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:white_check_mark: michaelstaib
:x: Pankraty
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[codecov[bot]]

Codecov Report

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

Project coverage is 77.38%. Comparing base (723733e) to head (c0670c7). Report is 1 commits behind head on main.

:exclamation: Current head c0670c7 differs from pull request most recent head 62815c4. Consider uploading reports for the commit 62815c4 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7065 +/- ## ========================================== + Coverage 77.27% 77.38% +0.10% ========================================== Files 2632 2627 -5 Lines 131349 131152 -197 ========================================== - Hits 101505 101490 -15 + Misses 29844 29662 -182 ``` | [Flag](https://app.codecov.io/gh/ChilliCream/graphql-platform/pull/7065/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ChilliCream) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ChilliCream/graphql-platform/pull/7065/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ChilliCream) | `77.38% <ø> (+0.10%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ChilliCream#carryforward-flags-in-the-pull-request-comment) to find out more.

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[michaelstaib]

Thanks for contributing.