Prometheus alertmanager – invalid leading UTF-8 octet – CentOS

I am trying to configure the slack notification from Prometheus alertmanager with below yml.

global:
  resolve_timeout: 1m
  slack_api_url: 'https://hooks.slack.com/services/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'

route:
  receiver: 'slack-notifications'

receivers:
- name: 'slack-notifications'
  slack_configs:
  - channel: '#monitoring-instances'
    send_resolved: true
    icon_url: https://avatars3.githubusercontent.com/u/3380462
    title: |-
     [{{ .Status | toUpper }}{{ if eq .Status "firing" }}:{{ .Alerts.Firing | len }}{{ end }}] {{ .CommonLabels.alertname }} for {{ .CommonLabels.job }}
     {{- if gt (len .CommonLabels) (len .GroupLabels) -}}
       {{" "}}(
       {{- with .CommonLabels.Remove .GroupLabels.Names }}
         {{- range $index, $label := .SortedPairs -}}
           {{ if $index }}, {{ end }}
           {{- $label.Name }}="{{ $label.Value -}}"
         {{- end }}
       {{- end -}}
       )
     {{- end }}
    text: >-
     {{ range .Alerts -}}
     *Alert:* {{ .Annotations.title }}{{ if .Labels.severity }} - `{{ .Labels.severity }}`{{ end }}

     *Description:* {{ .Annotations.description }}

     *Details:*
       {{ range .Labels.SortedPairs }} • *{{ .Name }}:* `{{ .Value }}`
       {{ end }}
     {{ end }}

When i start my alert-manager container it keep on restarting and shows below error.

alertmanager | level=error ts=2021-01-12T04:08:19.040Z caller=coordinator.go:124 component=configuration msg="Loading configuration file failed" file=/etc/alertmanager/alertmanager.yml err="yaml: invalid leading UTF-8 octet"

Have validated Here it shown as valid yaml

Also checked with notepad++ the encoding already showing as UTF-8 Any other way to fix this?

Even this code also shows same error.

  slack_configs:
  - channel: '#monitoring-instances'
    send_resolved: false
    title: '[{{ .Status | toUpper }}{{ if eq .Status "firing" }}:{{ .Alerts.Firing | len }}{{ end }}] Monitoring Event Notification'
    text: >-
      {{ range .Alerts }}
        *Alert:* {{ .Annotations.summary }} - `{{ .Labels.severity }}`
        *Description:* {{ .Annotations.description }}
        *Graph:* <{{ .GeneratorURL }}|:chart_with_upwards_trend:> *Runbook:* <{{ .Annotations.runbook }}|:spiral_note_pad:>
        *Details:*
        {{ range .Labels.SortedPairs }} • *{{ .Name }}:* `{{ .Value }}`
        {{ end }}
      {{ end }}

I am using Centos-8.2 system, is it something wrong in my system? Can anyone help me out here.