PR: Add constraint for pyqt5-sip on Python 3.8 (Dependencies)

[ccordoba12]

Description of Changes

• A new version of that package was released yesterday which broke compatibility with Python 3.8, even when the other PyQt5 packages still support it.
• Without this constraint Spyder fails to be installed in that Python version.
• This commit was already included in PR: Update spyder-kernels to 3.0.2 #23201 for the 6.x branch, but we also need to have it in master until we drop support for that Python version.

Issue(s) Resolved

Fixes #

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct:

[pep8speaks]

Hello @ccordoba12! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file setup.py:

Line 247:80: E501 line too long (106 > 79 characters)