Update dependency System.Text.Json to v9

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
System.Text.Json (source)	8.0.5 -> 9.0.0

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Configuration

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[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov[bot]]

Codecov Report

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

Project coverage is 78.60%. Comparing base (1c709bb) to head (f7253a1). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #152 +/- ## ========================================== + Coverage 76.38% 78.60% +2.22% ========================================== Files 9 9 Lines 326 472 +146 ========================================== + Hits 249 371 +122 - Misses 63 72 +9 - Partials 14 29 +15 ``` | [Flag](https://app.codecov.io/gh/christianhelle/httpgenerator/pull/152/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Christian+Helle) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/christianhelle/httpgenerator/pull/152/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Christian+Helle) | `78.60% <ø> (+2.22%)` | :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=Christian+Helle#carryforward-flags-in-the-pull-request-comment) to find out more.

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