Add a note about Qt6 installed from pip and libxcb errors #4876

Job	Run time
package-macos / package-macos (11, 3.12.1-macos11, 6178e42679eb83196240fc58b1438f481c32c2b0557f28ccf43aa7b1b80b7c4a)	3m 49s
package-pypi / pypi-sdist	47s
package-windows / package-windows (store-app)	3m 5s
package-pypi / pypi-bdist (macos-11, 3.9)	1m 16s
package-windows / package-windows (signed-app)	1m 32s
package-pypi / pypi-bdist (macos-11, 3.10)	1m 12s
package-windows / package-windows (installer)	3m 24s
package-pypi / pypi-bdist (macos-11, 3.11)	1m 14s
package-windows / package-windows (portable)	2m 45s
package-pypi / pypi-bdist (macos-11, 3.12)	1m 7s
package-pypi / pypi-bdist (windows-2019, 3.9)	2m 0s
package-pypi / pypi-bdist (windows-2019, 3.10)	1m 41s
package-pypi / pypi-bdist (windows-2019, 3.11)	1m 41s
package-pypi / pypi-bdist (windows-2019, 3.12)	1m 41s
package-pypi / pypi-release	0s
github-release	0s
	27m 14s

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