Update SLiM.spec to work with Qt 6 for Fedora and openSUSE #1261

Job	Run time
canceller	6s
tests-Windows-CLI (mingw64, x86_64, 3.8)	20m 25s
tests-Windows-CLI (ucrt64, ucrt-x86_64, 3.8)	20m 30s
tests-Unix-GUI (ubuntu-20.04, 5.9.5, 7)	4m 41s
tests-Unix-CLI (ubuntu-20.04, 7, 3.8)	9m 27s
tests-Windows-GUI (mingw64, x86_64)	12m 19s
tests-Unix-GUI (ubuntu-20.04, 5.15.2, 11)	5m 39s
tests-Unix-CLI (ubuntu-20.04, 11, 3.9)	9m 22s
tests-Windows-GUI (ucrt64, ucrt-x86_64)	12m 51s
tests-Unix-GUI (ubuntu-22.04, 5.15.2, 12)	6m 23s
tests-Unix-GUI (ubuntu-22.04, 6.7.2, 12)	6m 58s
tests-Unix-CLI (macos-12, 3.8)	12m 0s
tests-windows-latest-pacman (mingw64, x86_64)	1m 54s
tests-Unix-GUI (macos-12, 5.9.5)	5m 56s
tests-Unix-CLI (macos-13, 3.9)	15m 35s
tests-windows-latest-pacman (ucrt64, ucrt-x86_64)	1m 58s
tests-Unix-GUI (macos-13, 5.15.2)	6m 48s
tests-Unix-GUI (macos-13, 6.7.2)	7m 51s
	2h 40m 43s

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