ci: Don't install Qt when running on self-hosted #40

Job	Run time
build (ubuntu-24.04, ci-release-static-qt5, 5.15)	3m 37s
build (ubuntu-24.04, ci-dev-static-qt5, 5.15)	26m 57s
build (ubuntu-24.04, ci-python-qt6, 6.6.0)	4m 19s
build (ubuntu-24.04, ci-release-static-qt6, 6.3.*)	3m 46s
build (ubuntu-24.04, ci-dev-static-qt6, 6.3.*)	23m 42s
build (windows-2022, ci-release-static-qt5, 5.15)	3m 55s
build (windows-2022, ci-dev-static-qt5, 5.15)	4m 40s
build (windows-2022, ci-python-qt6, 6.6.0)	1m 18s
build (windows-2022, ci-release-static-qt6, 6.3.*)	4m 49s
build (windows-2022, ci-dev-static-qt6, 6.3.*)	6m 39s
build (windows-2019, ci-release-static-qt5, 5.15)	3m 23s
build (windows-2019, ci-dev-static-qt5, 5.15)	4m 34s
build (windows-2019, ci-python-qt6, 6.6.0)	5m 28s
build (windows-2019, ci-release-static-qt6, 6.3.*)	4m 51s
build (windows-2019, ci-dev-static-qt6, 6.3.*)	5m 50s
build (macos-13, ci-release-static-qt5, 5.15)	3m 5s
build (macos-13, ci-dev-static-qt5, 5.15)	4m 35s
build (macos-13, ci-python-qt6, 6.6.0)	5m 48s
build (macos-13, ci-release-static-qt6, 6.3.*)	5m 1s
build (macos-13, ci-dev-static-qt6, 6.3.*)	6m 53s
build (ubuntu-24.04, ci-clang-tidy-qt6, 6.3.*)	5m 34s
build (ubuntu-24.04, clazy, --preset=clazy, 5.15)	2m 21s
build (ubuntu-24.04, ci-dev-valgrind-qt5, 5.15)	24m 28s
build (ubuntu-24.04, ci-dev-valgrind-qt6, 6.5.*)	25m 30s
	3h 11m 3s

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