[INFRA,DOC] Update to doxygen 1.9.6

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Name	Status	Preview	Updated
seqan3	✅ Ready (Inspect)	Visit Preview	Jan 2, 2023 at 4:30PM (UTC)

[codecov[bot]]

Codecov Report

Base: 98.22% // Head: 98.22% // No change to project coverage :thumbsup:

Coverage data is based on head (3732168) compared to base (d2400a9). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3116 +/- ## ======================================= Coverage 98.22% 98.22% ======================================= Files 275 275 Lines 12192 12192 ======================================= Hits 11975 11975 Misses 217 217 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan)

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