build(deps): bump System.Collections.Immutable from 7.0.0 to 9.0.0

Bumps [System.Collections.Immutable](https://github.com/dotnet/runtime) from 7.0.0 to 9.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v7.0.0...v9.0.0)

---
updated-dependencies:
- dependency-name: System.Collections.Immutable
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

APIMatic.Core/APIMatic.Core.csproj

@@ -37,7 +37,7 @@
             <PrivateAssets>all</PrivateAssets>
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>
-        <PackageReference Include="System.Collections.Immutable" Version="7.0.0" />
+        <PackageReference Include="System.Collections.Immutable" Version="9.0.0" />
         <PackageReference Include="Newtonsoft.Json" Version="[13.0.1,)" />
     </ItemGroup>
     <ItemGroup>