Remove cloudstorages/id/content endpoint

[Marishka17]

Motivation and context

We discussed that support of the previous version of CS content endpoint would be terminated in version 2.6.0

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into the CHANGELOG file
• I have updated the documentation accordingly
  - [ ] I have added tests to cover my changes
  - [ ] I have linked related issues (see 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.

[nmanovic]

@Marishka17 , need to add changelog.

[nmanovic]

@Marishka17 , could you please resolve conflicts?

[codecov]

Codecov Report

Merging #6946 (e961118) into develop (6ae1cff) will increase coverage by 0.00%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #6946   +/-   ##
========================================
  Coverage    81.42%   81.42%           
========================================
  Files          364      364           
  Lines        39904    39874   -30     
  Branches      3699     3699           
========================================
- Hits         32491    32468   -23     
+ Misses        7413     7406    -7     

Components	Coverage Δ
cvat-ui	75.49% <ø> (-0.03%)	⬇️
cvat-server	86.99% <ø> (+0.03%)	⬆️