Update ESXi example in metricshub-example.yaml

[NassimBtk]

Specification

The vCenter example is not clear, we think we are monitoring a vCenter, but we are actually talking about an ESXi.

  #═══════════════════════════════════════════════════
  # vCenter WBEM configuration            
  #═══════════════════════════════════════════════════

  # server-11:
  #   attributes:
  #     host.name: server-11
  #     host.type: oob
  #   protocols:
  #     wbem:
  #       protocol: https
  #       port: 5989
  #       timeout: 120
  #       username: admin
  #       password: password
  #       vcenter: server-vcenter

Update the message as the following:

  #═══════════════════════════════════════════════════
  # ESXi Host Configuration through WBEM service
  # Authentication certificate will be requested
  # from the specified VMware vCenter server
  #═══════════════════════════════════════════════════

  # server-11:
  #   attributes:
  #     host.name: server-11
  #     host.type: oob
  #   protocols:
  #     wbem:
  #       protocol: https
  #       port: 5989
  #       timeout: 120
  #       username: admin
  #       password: password
  #       vcenter: vcenter-server # Optional, for multi-tier authentication only