overrides: multidict -> remove pip dependency

[Kiskae]

This appears to have been added in #1329 without comment, but is now causing a duplicate dependency failure for me:

python3.11-multidict> Found duplicated packages in closure for dependency 'pip':
python3.11-multidict>   pip 23.2.1 (/nix/store/slhj69him45n2pck7wkknnffi4ay0jy0-python3.11-pip-23.2.1/lib/python3.11/site-packages/pip-23.2.1.dist-info)
python3.11-multidict>   pip 23.2.1 (/nix/store/rqch5axq9ky53cny22zwyvq93g0w68jn-python3.11-pip-23.2.1/lib/python3.11/site-packages/pip-23.2.1.dist-info)
python3.11-multidict> Package duplicates found in closure, see above. Usually this happens if two packages depend on different version of the same dependency.

Contribution checklist (recommended but not always applicable/required):

• There's an automated test for this change
• Commit messages or code include references to related issues or PRs (including third parties)
• Commit messages are conventional - examples from the log include "feat: add changelog files to fixup hook", "fix(contourpy): allow wheel usage", and "test: add sqlalchemy2 test"

[tfc]

thumbs up!