Update Pyrra to 0.4.2

Pyrra 0.4.1 is crashing at start time and the fixed version is 0.4.2 so we should change the verison used

See the issue in Pyrra repository: https://github.com/pyrra-dev/pyrra/issues/324

jsonnet/kube-prometheus/versions.json

@@ -9,5 +9,5 @@
   "prometheusOperator": "0.57.0",
   "kubeRbacProxy": "0.12.0",
   "configmapReload": "0.5.0",
-  "pyrra": "0.4.1"
+  "pyrra": "0.4.2"
 }