Replace xml.etree.ElementTree with defusedxml

[wonjuleee]

Summary

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-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (04dff62) 79.98% compared to head (9b19109) 79.98%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1117   +/-   ##
========================================
  Coverage    79.98%   79.98%           
========================================
  Files          258      258           
  Lines        29300    29300           
  Branches      5740     5740           
========================================
+ Hits         23435    23437    +2     
  Misses        4515     4515           
+ Partials      1350     1348    -2     

Flag	Coverage Δ
macos-11_Python-3.8	79.08% <100.00%> (ø)
ubuntu-20.04_Python-3.8	79.97% <100.00%> (ø)
windows-2019_Python-3.8	79.90% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/datumaro/plugins/data_formats/roboflow/base.py	86.30% <100.00%> (ø)
...datumaro/plugins/data_formats/roboflow/importer.py	83.96% <100.00%> (ø)

... and 2 files with indirect coverage changes

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[vinnamkim]

LGTM.