Adjust `InfoInhibitor` severity

[RiRa12621]

kube-prometheus/jsonnet/kube-prometheus/components/mixin/alerts/general.libsonnet

Line 51 in 3dd3bb6

severity: 'none',

sets the severity to none, which on its own makes sense, but apparently PagerDuty thinks that anything that doesn't come in on a valid severity, should be high urgency, which defies the purpose of this alert.

https://support.pagerduty.com/main/docs/dynamic-notifications#severity-and-urgency-mapping

Best would probably be to make this Info level itself. Happy to contribute that if we agree on it.

[simonpasquier]

we can probably make the value of the 'none' severity configurable.