reduce severity level to warning (#28939)

Signed-off-by: bergquist <carl.bergquist@gmail.com>

grafana-mixin/alerts/alerts.yaml

 groups:
-- name: GrafanaAlerts
-  rules:
-  - alert: GrafanaRequestsFailing
-    for: 5m
-    expr: |
-      100 * namespace_job_handler_statuscode:http_request_total:rate5m{handler!~"/datasources/proxy/:id.*|/ds/query|/tsdb/query", statuscode=~"5.."}
-      /
-      namespace_job_handler_statuscode:http_request_total:rate5m{handler!~"/datasources/proxy/:id.*|/ds/query|/tsdb/query"}
-      > 0.5
-    labels:
-      severity: 'critical'
-    annotations:
-      message: "'{{ $labels.namespace }}' / '{{ $labels.job }}' / '{{ $labels.handler }}' is experiencing {{ $value | humanize }}% errors"
+  - name: GrafanaAlerts
+    rules:
+      - alert: GrafanaRequestsFailing
+        for: 5m
+        expr: |
+          100 * namespace_job_handler_statuscode:http_request_total:rate5m{handler!~"/datasources/proxy/:id.*|/ds/query|/tsdb/query", statuscode=~"5.."}
+          /
+          namespace_job_handler_statuscode:http_request_total:rate5m{handler!~"/datasources/proxy/:id.*|/ds/query|/tsdb/query"}
+          > 0.5
+        labels:
+          severity: 'warning'
+        annotations:
+          message: "'{{ $labels.namespace }}' / '{{ $labels.job }}' / '{{ $labels.handler }}' is experiencing {{ $value | humanize }}% errors"