switch to PySide6==6.7.3 and force dpi to 96 for windows #881

Job	Run time
Python 3.11 on macos-latest PyQt6 wheel	3m 37s
Python 3.10 on ubuntu-latest PyQt5 wheel	4m 54s
Python 3.12 on macos-latest PySide6 wheel (for MacOS binaries)	4m 55s
Python 3.13 on windows-latest PyQt6 wheel	4m 44s
Python 3.9 on ubuntu-latest (Minimum Versions)	5m 10s
Python 3.13 on windows-latest PySide6 wheel (for Windows binaries)	4m 23s
Python 3.10 on ubuntu-latest PySide6 wheel	3m 14s
	30m 57s

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