mapillary_vistas_format: fix image import

[IRDonch]

Summary

This module ended up with a broken import due to #537 and #538 being merged at roughly the same time.

How to test

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues

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

[zhiltsov-max]

It looks like the real problem is that https://www.python.org/dev/peps/pep-0562/ is only valid from py3.7.