update document regarding installation command from github

[jihyeonyi]

Summary

installation command is updated.
before: pip install 'git+https://github.com/openvinotoolkit/datumaro[default]'
after: pip install 'datumaro[default] @ git+https://github.com/openvinotoolkit/datumaro'

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

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) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e7f6fea) 80.08% compared to head (753faaf) 80.07%.

❗ Current head 753faaf differs from pull request most recent head 951f648. Consider uploading reports for the commit 951f648 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1202      +/-   ##
===========================================
- Coverage    80.08%   80.07%   -0.01%     
===========================================
  Files          268      268              
  Lines        29865    29865              
  Branches      5846     5846              
===========================================
- Hits         23916    23915       -1     
  Misses        4617     4617              
- Partials      1332     1333       +1     

Flag	Coverage Δ
macos-11_Python-3.8	79.19% <ø> (-0.01%)	⬇️
ubuntu-20.04_Python-3.8	80.06% <ø> (ø)
windows-2022_Python-3.8	80.04% <ø> (ø)

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[wonjuleee]

LGTM

[vinnamkim]

LGTM.