Move webhook_config to the slack-alerts-ticket receiver for Alertmanager (#1095)

* Moves webhook_config to the slack-alerts-ticket receiver

When I added the slack-fyis receiver last year I accidentally moved the
webhook_config section of the slack-alerts-ticket receiver to the new
slack-fyis receiver. The outcome is that alerts stopped being routed to the
alertmanager-github-receiver service which is responsible for creating Github
issuse in the ops-tracker repository for production alerts.

* Updates configmap-reload container to 0.9.0 in alertmanager pod

A while ago when I updated the Alertmanager config, the build updated the
Alertmanager configmap. When the configmap-reload container noticed the
configmap was updated it tried to restart the Alertmanager container, but got
"x509: certificate signed by unknown authority". This used to work, so I'm not
sure what changed. I'm attempting to update the configmap-reload container in
the hope that perhaps the maintainer perhaps updated the ca-certificates in the
container image.

* Updates configmap-reload in alertmanager pod to v0.15.0

The previous commit (@530986f) updated configmap-reload to 0.9.0, but I then
realized that the repo was no longer publishing updated images to Docker Hub,
but instead to Github Container Registry. This commit changes the image repo
and updates to the latest.

With this update in place, reloads are now working again.

* Updates a comment to reflect ghcr.io instead of hub.docker.com

Author: nkinkade

config/federation/alertmanager/config.yml.template

@@ -142,6 +142,10 @@ receivers:
           {{- printf "}" | urlquery }}
         {{- end -}}
 
+  # All alerts sent to slack are also sent to the github webhook receiver.
+  webhook_configs:
+  - url: '{{GITHUB_RECEIVER_URL}}'
+
 - name: 'slack-fyis'
   slack_configs:
   - send_resolved: false
@@ -187,10 +191,6 @@ receivers:
           {{- printf "}" | urlquery }}
         {{- end -}}
 
-  # All alerts sent to slack are also sent to the github webhook receiver.
-  webhook_configs:
-  - url: '{{GITHUB_RECEIVER_URL}}'
-
 - name: 'pagerduty-pages'
   pagerduty_configs:
   - send_resolved: true

k8s/prometheus-federation/deployments/alertmanager.yml

@@ -56,9 +56,9 @@ spec:
         - mountPath: /etc/alertmanager
           name: alertmanager-config
 
-      # Check https://hub.docker.com/r/jimmidyson/configmap-reload/tags/ for the current
+      # Check https://ghcr.io/jimmidyson/configmap-reload/tags/ for the current
       # stable version.
-      - image: jimmidyson/configmap-reload:v0.7.1
+      - image: ghcr.io/jimmidyson/configmap-reload:v0.15.0
         name: configmap-reload
         args: ["-webhook-url", "$(ALERTMGR_RELOAD_URL)", "-volume-dir", "/alertmanager-config"]
         env: