Bump CSharpier.Core and System.Text.Json

Bumps [CSharpier.Core](https://github.com/belav/csharpier) and System.Text.Json. These dependencies needed to be updated together.

Updates `CSharpier.Core` from 0.28.2 to 0.29.0
- [Release notes](https://github.com/belav/csharpier/releases)
- [Changelog](https://github.com/belav/csharpier/blob/main/CHANGELOG.md)
- [Commits](belav/csharpier@0.28.2...0.29.0)

Updates `System.Text.Json` from 8.0.0 to 8.0.4

---
updated-dependencies:
- dependency-name: CSharpier.Core
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: System.Text.Json
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

src/ApiGenerator/ApiGenerator.csproj

@@ -9,7 +9,7 @@
     <PreserveCompilationContext>true</PreserveCompilationContext>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="CSharpier.Core" Version="0.28.2" />
+    <PackageReference Include="CSharpier.Core" Version="0.29.0" />
     <PackageReference Include="Glob" Version="1.1.9" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageReference Include="NSwag.Core" Version="14.1.0" />