[MNT]: CI: cleanup: remove stale/outdated version range restrictions

[jayaddison]

Summary

A large portion of our GitHub Actions CI tests.yml workflow matrix is composed of version range restrictions for Python packages:

matplotlib/.github/workflows/tests.yml

Lines 48 to 108 in 7d5d027

	matrix:
	include:
	- name-suffix: "(Minimum Versions)"
	os: ubuntu-22.04
	python-version: '3.11'
	extra-requirements: '-c requirements/testing/minver.txt'
	delete-font-cache: true
	# https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html
	pyqt6-ver: '!=6.6.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	- os: ubuntu-22.04
	python-version: '3.11'
	CFLAGS: "-fno-lto" # Ensure that disabling LTO works.
	# https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html
	pyqt6-ver: '!=6.6.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	extra-requirements: '-r requirements/testing/extra.txt'
	- os: ubuntu-22.04-arm
	python-version: '3.12'
	# https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html
	pyqt6-ver: '!=6.6.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	- os: ubuntu-22.04
	python-version: '3.13'
	# https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html
	pyqt6-ver: '!=6.6.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	- name-suffix: "Free-threaded"
	os: ubuntu-22.04
	python-version: '3.13t'
	# https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html
	pyqt6-ver: '!=6.6.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	- os: ubuntu-24.04
	python-version: '3.12'
	# https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html
	pyqt6-ver: '!=6.6.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	- os: macos-13 # This runner is on Intel chips.
	# merge numpy and pandas install in nighties test when this runner is dropped
	python-version: '3.10'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	- os: macos-14 # This runner is on M1 (arm64) chips.
	python-version: '3.12'
	# https://github.com/matplotlib/matplotlib/issues/29732
	pygobject-ver: '<3.52.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'
	- os: macos-14 # This runner is on M1 (arm64) chips.
	python-version: '3.13'
	# https://github.com/matplotlib/matplotlib/issues/29732
	pygobject-ver: '<3.52.0'
	# https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
	pyside6-ver: '!=6.5.1'

I think that most of these can now safely be removed.

In practice, three variables are currently declared in the workflow file:

$ grep ' .*-ver: ' .github/workflows/tests.yml | sort | uniq
            pygobject-ver: '<3.52.0'
            pyqt6-ver: '!=6.6.0'
            pyside6-ver: '!=6.5.1'

Proposed fix

Remove the version pin variables and template evaluation for:

• pyside2-ver
• pyqt6-ver
• pyside6-ver

[jayaddison]

Proposed fix

Remove the version pin variables and template evaluation for:

• pyside2-ver
• pyqt6-ver
• pyside6-ver

One more: we can also remove a template reference to pyqt5-ver.

After the cleanup, only one (1) variable, pygobject-ver, should remain.