Update dependency System.Collections.Immutable to v9

Author: renovate-bot

EnumerableAsyncProcessor/EnumerableAsyncProcessor.csproj

@@ -37,7 +37,7 @@
           <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>
 
-        <PackageReference Include="System.Collections.Immutable" Version="8.0.0" />
+        <PackageReference Include="System.Collections.Immutable" Version="9.0.0" />
 
     </ItemGroup>