eng: upgrade test project target framework from net9.0 to net10.0

The repository already uses .NET 10 SDK (10.0.102 in global.json).
Aligning the test project target framework with the installed SDK
ensures tests run on the current .NET runtime.

All 5013 tests pass on net10.0.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net9.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
   </PropertyGroup>