Merged PR 42441: Add direct references to S.T.J in tools

#### AI description  (iteration 1)
#### PR Classification
Dependency update

#### PR Summary
This pull request adds a direct reference to `System.Text.Json` in the project.
- Added `System.Text.Json` reference in `src/Tools/dotnet-user-secrets/src/dotnet-user-secrets.csproj`

Author: wtgodbe

src/Tools/dotnet-user-secrets/src/dotnet-user-secrets.csproj

@@ -21,6 +21,7 @@
 
   <ItemGroup>
     <Reference Include="Newtonsoft.Json" />
+    <Reference Include="System.Text.Json" />
     <Reference Include="Microsoft.Extensions.Configuration.UserSecrets" />
   </ItemGroup>