switch to plasma5 #85

Job	Run time
generate_matrix	1m 1s
update_flake	48s
check_flake	9m 51s
build_images (x86_64, linux, server, proxmox)	10m 41s
build_images (x86_64, linux, server, raw-efi)	9m 45s
build_images (x86_64, linux, server, iso)	10m 59s
build_images (x86_64, linux, bri, proxmox)	17m 29s
build_images (x86_64, linux, bri, raw-efi)	17m 55s
build_images (x86_64, linux, bri, iso)	15m 59s
build_flake (cb)	1m 44s
build_flake (pyEnv)	1m 29s
build_flake (sysdo)	1m 40s
push_update	0s
	1h 39m 21s

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