[DOCS] Update Endpoint Security screenshots

[jmikell821]

Related issue: #2025

We need to update all .pngs and/or gifs that reference the former Endpoint Security integration and update it with the new one:

Topics:

• Install Endpoint Security integration
  • security-integration.png
  • add-elastic-endpoint-security.png
  • add-agent.png
  • endpoint-configuration.png