Fix #424

[lol768]

v7.12.0 changed the default csharp library to generichost, so updating the generator is all that is required.

See https://github.com/OpenAPITools/openapi-generator/releases/tag/v7.12.0

This PR fixes #424

Checklist

• I have read the contributing guidelines
  and signed the CLA.
• I have referenced an issue containing the design document if my change
  introduces a new feature. Not applicable, not a new feature
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
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  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works. Not applicable, would expect unit tests within upstream openapi-generator codebase
• I have added the necessary documentation within the code base (if
  appropriate).
  • Happy to be guided by maintainers' views here.

Further comments

I am hopeful that the decision from upstream (openapi-generator) to change the default here will add some weight to the reasoning I provided in #424

[aeneasr]

Amazing, thanks!