Fixed example of configmap containing alertmanager config

alertmanager-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
name: alertmanager-conf
labels:
    name: alertmanager-conf
namespace: monitoring
data:
  alertmanager.yml: |-
      global:
        # slack_api_url: ''
        resolve_timeout: 20s
   
      receivers:
        - name: default-receiver
          # slack_configs:
          #  - channel: '@you'
          #    send_resolved: true
        - name: 'webhook'
          webhook_configs:
            - send_resolved: true
              url: ''
      route:
        group_wait: 10s
        group_interval: 5m
        receiver: webhook
        repeat_interval: 3h