Only use .net8 in tests

Author: mburumaxwell

tests/Directory.Build.props

@@ -3,6 +3,7 @@
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory).., '$(MSBuildThisFileName)$(MSBuildThisFileExtension)'))\$(MSBuildThisFileName)$(MSBuildThisFileExtension)" />
 
   <PropertyGroup>
+    <TargetFrameworks>net8.0</TargetFrameworks>
     <IsTestProject>true</IsTestProject>
     <IsPackable>false</IsPackable>
   </PropertyGroup>

tests/Tingle.PeriodicTasks.AspNetCore.Tests/Tingle.PeriodicTasks.AspNetCore.Tests.csproj

@@ -1,8 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="7.0.0" Condition="'$(TargetFramework)' == 'net7.0'"/>
-    <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.0" Condition="'$(TargetFramework)' == 'net8.0'"/>
+    <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.0" />
   </ItemGroup>
 
   <ItemGroup>