Use correct service name in LDAP authentication documentation

[RyanHir]

Update documentation to use the proper service when enabling LDAP authentication.

Motivation and context

The current documentation references a service (cvat) that is now renamed to cvat_server. This change makes this apparent.

How has this been tested?

Used the same configs as described in the guide with a Windows Server 2022 instance, and only deviated from the instructions as to select the correct docker service. This PR has this change.

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into the CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (see GitHub docs)
• I have increased versions of npm packages if it is necessary
  (cvat-canvas,
  cvat-core,
  cvat-data and
  cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[nmanovic]

@RyanHir , thanks for the contribution!