Cypress test. Creating a label with existing label name.

[dvkruchinin]

Motivation and context

Add cypress test. Creating a label with existing label name.

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (read 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.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2021 Intel Corporation
#
# SPDX-License-Identifier: MIT

[coveralls]

Coverage remained the same at 70.321% when pulling 9030a7a on dvkruchinin:dkru/case-43-create-label-with-existing-label-name into 3ced77c on openvinotoolkit:develop.