ci: fix test to run on .net 10 only

Author: chyyran

src/VCDiff.Tests/VCDiff.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp3.0;netcoreapp3.1;net5.0;net6.0</TargetFrameworks>
+    <TargetFramework>net10.0</TargetFramework>
     <IsPackable>false</IsPackable>
     <LangVersion>latest</LangVersion>
   </PropertyGroup>