Remove MODELS_ROOT and the corresponding mountpoints

[SpecLad]

Motivation and context

This appears to be a vestigial directory left behind from e7585b8.

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have created a changelog fragment
• [ ] I have updated the documentation accordingly
• [ ] I have added tests to cover my changes
• [ ] I have linked related issues (see GitHub docs)

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.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.33%. Comparing base (715ced2) to head (5861643).
⚠️ Report is 5 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #9773      +/-   ##
===========================================
+ Coverage    79.33%   82.33%   +2.99%     
===========================================
  Files          466      466              
  Lines        48228    48361     +133     
  Branches      4082     4082              
===========================================
+ Hits         38262    39816    +1554     
+ Misses        9966     8545    -1421     

Components	Coverage Δ
cvat-ui	77.26% <ø> (ø)
cvat-server	86.20% <ø> (+5.27%)	⬆️

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