Update System.Collections.Immutable version to SdkPackageVersion

Author: mikaelweave

Directory.Packages.props

@@ -131,7 +131,7 @@
     <PackageVersion Include="prometheus-net.DotNetRuntime" Version="4.4.1" />
     <PackageVersion Include="prometheus-net.SystemMetrics" Version="3.1.0" />
     <PackageVersion Include="StyleCop.Analyzers" Version="1.2.0-beta.556" />
-    <PackageVersion Include="System.Collections.Immutable" Version="9.0.1" />
+    <PackageVersion Include="System.Collections.Immutable" Version="$(SdkPackageVersion)" />
     <PackageVersion Include="System.CommandLine.NamingConventionBinder" Version="2.0.0-beta4.22272.1" />
     <PackageVersion Include="System.CommandLine" Version="2.0.0-beta4.22272.1" />
     <PackageVersion Include="System.Configuration.ConfigurationManager" Version="$(SdkPackageVersion)" />