chore(deps): update dotnet monorepo to v8 (major) (#100)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Diff for: src/OpenFeature.Contrib.Providers.Flagd/OpenFeature.Contrib.Providers.Flagd.csproj

@@ -19,7 +19,7 @@
     </AssemblyAttribute>
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'net462'">
-    <PackageReference Include="System.Net.Http.WinHttpHandler" Version="7.0.0" />
+    <PackageReference Include="System.Net.Http.WinHttpHandler" Version="8.0.0" />
   </ItemGroup>
   <ItemGroup>
     <!-- The schema.proto file referenced here will be used to automatically generate the Grpc client when executing 'dotnet build' -->

Diff for: src/OpenFeature.Contrib.Providers.GOFeatureFlag/OpenFeature.Contrib.Providers.GOFeatureFlag.csproj

@@ -13,7 +13,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="System.Text.Json" Version="7.0.4" />
+    <PackageReference Include="System.Text.Json" Version="8.0.0" />
   </ItemGroup>
 
   <PropertyGroup>