Update dependency System.Text.Json to v9

Author: dependencyupdates[bot]

src/ServicePulse.Host.Tests/ServicePulse.Host.Tests.csproj

@@ -14,7 +14,7 @@
     <PackageReference Include="NUnit" Version="4.4.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="5.1.0" />
     <PackageReference Include="Particular.Approvals" Version="1.1.1" />
-    <PackageReference Include="System.Text.Json" Version="8.0.5" />
+    <PackageReference Include="System.Text.Json" Version="9.0.9" />
   </ItemGroup>
 
   <ItemGroup>