Bump System.Collections.Immutable from 8.0.0 to 9.0.0 in /src

Bumps [System.Collections.Immutable](https://github.com/dotnet/runtime) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v8.0.0...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]>

Author: dependabot[bot]

src/Directory.Packages.props

@@ -15,7 +15,7 @@
     <PackageVersion Include="Resourcer.Fody" Version="1.8.1" />
     <PackageVersion Include="Serilog" Version="4.1.0" />
     <PackageVersion Include="Serilog.Sinks.File" Version="6.0.0" />
-    <PackageVersion Include="System.Collections.Immutable" Version="8.0.0" />
+    <PackageVersion Include="System.Collections.Immutable" Version="9.0.0" />
     <PackageVersion Include="System.Globalization.Extensions" Version="4.3.0" />
     <PackageVersion Include="System.IO.Compression" Version="4.3.0" />
     <PackageVersion Include="System.Management" Version="9.0.0" />