Patch requirements matplotlib

[McBs]

Description

Update matplotlib version in setup.py and requirements

• Set matplotlib version to 3.9.0 instead of 3.9.1 due to CI issues

Checklist

• [ ] ~This pull request is associated to an issue~
• [x] This PR contains a description
• [ ] ~Did you add a new method? If so, you need to~
  • [ ] ~add method description~
  • [ ] ~maybe mention class in the corresponding __init__~
  • [ ] ~add an example using the method in examples/advanced_flows/ or examples/simple_flows/~
  • [ ] ~add a test in tests/~
• [x] Add someone else as reviewer and wait for approval before merging.

[pep8speaks]

Hello @McBs! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file setup.py:

Line 15:80: E501 line too long (114 > 79 characters)