Kubernetes installation docs still link to nerdswords repository

The documentation [here](https://github.com/prometheus-community/yet-another-cloudwatch-exporter/blob/master/docs/installation.md#install-with-helm) still links to https://github.com/nerdswords/helm-charts.

The link could be changed to here: https://github.com/prometheus-community/helm-charts/tree/main/charts/prometheus-yet-another-cloudwatch-exporter