Depolarizing channel on gpu

[AlejandroSopena]

I updated CUDA and cupy on my machine and I realised that the depolarizing channel raises a TypeError when applying it to density matrix circuits and running them on gpu with qibojit-cupy using the latest version of cupy (cupy-cuda12x). This PR fixes it.

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.

[codecov]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage 👍

Coverage data is based on head (cfba10c) compared to base (80139d4).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #769   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           94        94           
  Lines        12460     12460           
=========================================
  Hits         12460     12460           

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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

Impacted Files	Coverage Δ
src/qibo/gates/channels.py	100.00% <100.00%> (ø)

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[scarrazza]

Thank you @AlejandroSopena. When running tests on GPU, I am getting errors in src/qibo/tests/test_measurements.py. Have you observed this issue too?

[AlejandroSopena]

Yes, I can reproduce that issue as well. I have already fixed it and I need to open a PR in qibojit but it seems that I don't have permissions to push.

[scarrazza]

Thank you. You should have access now.

[AlejandroSopena]

Thanks. Fixed in qiboteam/qibojit#101