many-to-one requires explicit grouping (#58174)

The current query results in a many-to-one relationship which requires explicit grouping see more details here
https://github.com/portefaix/portefaix-hub/pull/306

https://prometheus.io/docs/prometheus/latest/querying/operators/#many-to-one-and-one-to-many-vector-matches

grafana-mixin/alerts/alerts.libsonnet

@@ -12,7 +12,7 @@
             alert: 'GrafanaRequestsFailing',
             expr: |||
               100 * namespace_job_handler_statuscode:grafana_http_request_duration_seconds_count:rate5m{handler!~"/api/datasources/proxy/:id.*|/api/ds/query|/api/tsdb/query", status_code=~"5.."}
-              / ignoring (status_code)
+              / ignoring (status_code) group_left
               sum without (status_code) (namespace_job_handler_statuscode:grafana_http_request_duration_seconds_count:rate5m{handler!~"/api/datasources/proxy/:id.*|/api/ds/query|/api/tsdb/query"})
               > %(grafanaRequestsFailingThresholdPercent)s
             ||| % $._config,