[Security Solution] Change max_signals limit warning to informational

[approksiu]

Epics/Issues:
#179680
#173593

Summary

If a detection rule has a max_signal setting set to a number higher than xpack.alerting.rules.run.alerts.max, we show a warning that there is a mismatch.

We need to change the severity of this notice to informational.

• While the mismatch is there, it does not necessarily mean that the rule will hit the limit.
• Users don't necessarily need to take any action.
• In case the rule hits the limit - we generate other warning, and it makes sense to action it then.

To do

[elasticmachine]

Pinging @elastic/security-detection-rule-management (Team:Detection Rule Management)

[approksiu]

This issue will be superseeded.