build: Fix nuget version for Microsoft.AspNetCore.Mvc.Testing for old SDK versions

Author: NelsonBN

tests/PowerUtils.AspNetCore.ErrorHandler.Tests/PowerUtils.AspNetCore.ErrorHandler.Tests.csproj

@@ -54,10 +54,10 @@
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="7.0.7" />
   </ItemGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'net6.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="[7.0.7]" allowedVersions="[7.0.7]" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="[6.0.18]" allowedVersions="[6.0.18]" />
   </ItemGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'net5.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="[7.0.7]" allowedVersions="[7.0.7]" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="[5.0.17]" allowedVersions="[5.0.17]" />
   </ItemGroup>