ci(renovate): Disable NuGet package manager updates

Avoid bogus updates of NuGet test projects which should be prevented by
ignoring "**/src/funTest/assets/**" already, but that stopped to work.

Signed-off-by: Sebastian Schuberth <sebastian@doubleopen.org>

renovate.json

@@ -42,5 +42,8 @@
       "matchManagers": ["npm"],
       "schedule": "after 9pm on sunday"
     }
-  ]
+  ],
+  "nuget": {
+    "enabled": false
+  }
 }