Remove dependency on sip

[gillins]

Checklist

• [ ] Used a personal fork of the feedstock to propose changes
• [ ] Bumped the build number (if the version is unchanged)
• [ ] Re-rendered with the latest conda-smithy (Use the phrase code>@<space/conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• [ ] Ensured the license file is being packaged.

pyqt contains its own version of sip so depending on the sip package is not needed. In fact it appears to be causing problems since the version of sip in pyqt is a bit older (and needs to be) so installing both is a problem.

xref: https://github.com/conda-forge/pyqt-feedstock/pull/91#issuecomment-741592391

[gillins]

@conda-forge-admin, please rerender

[gillins]

@conda-forge-admin, please rerender

[dschreij]

Thanks!