Bump rancher-project-monitoring images

[alexandreLamarre]

bump alertmanager to v0.26
bump grafana to v9.5.14

Related Issue:

Requires rancher/image-mirror#540

Checklist

Please fill out this table to identify which fields need to be modified in your PR.

Under Status, either indicate Does Not Apply or Added to this PR.

Version to be incremented	Why should this be modified?	Status
version in rancher-project-monitoring package.yaml	You modified the contents of the rancher-project-monitoring chart to make changes	TODO: will add this to the PR
helmProjectOperator.image.tag in prometheus-federator values.yaml	Either you modified the rancher-project-monitoring chart or you modified the main.go file	Does not apply
appVersion in prometheus-federator Chart.yaml	You modified the helmProjectOperator.image.tag in the above box	Does not apply
version in prometheus-federator Chart.yaml	Either you modified the appVersion in the above box or you modified the contents of the prometheus-federator chart to make changes	Does not apply