chore(deps): bump System.Text.Json from 5.0.2 to 8.0.0

Bumps [System.Text.Json](https://github.com/dotnet/runtime) from 5.0.2 to 8.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v5.0.2...v8.0.0)

---
updated-dependencies:
- dependency-name: System.Text.Json
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

src/MockHttp.Json/MockHttp.Json.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>net7.0;net6.0;netstandard2.1;netstandard2.0;net48;net472;net462</TargetFrameworks>
@@ -20,7 +20,7 @@
   <ItemGroup>
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" Condition="$(TargetFramework.StartsWith('net4')) Or '$(TargetFramework)'=='netstandard2.0' Or '$(TargetFramework)'=='netstandard2.1'" />
-    <PackageReference Include="System.Text.Json" Version="5.0.2" Condition="$(TargetFramework.StartsWith('net4')) Or '$(TargetFramework)'=='netstandard2.0' Or '$(TargetFramework)'=='netstandard2.1'" />
+    <PackageReference Include="System.Text.Json" Version="8.0.0" Condition="$(TargetFramework.StartsWith('net4')) Or '$(TargetFramework)'=='netstandard2.0' Or '$(TargetFramework)'=='netstandard2.1'" />
   </ItemGroup>
 
   <ItemGroup>