Remove .NET 7 and F38. (#349) #587

Job	Run time
Verify tests pass (docker.io/library/alpine:latest, 6.0)	7m 16s
Verify tests pass (docker.io/library/alpine:edge, 6.0)	7m 27s
Verify tests pass (docker.io/library/alpine:edge, 8.0)	8m 11s
Verify tests pass (quay.io/centos/centos:stream8, 6.0)	8m 42s
Verify tests pass (quay.io/centos/centos:stream8, 8.0)	43s
Verify tests pass (quay.io/centos/centos:stream9, 6.0)	7m 15s
Verify tests pass (quay.io/centos/centos:stream9, 8.0)	26s
Verify tests pass (registry.fedoraproject.org/fedora:39, 6.0)	10m 13s
Verify tests pass (registry.fedoraproject.org/fedora:39, 8.0)	8m 57s
Verify tests pass (registry.fedoraproject.org/fedora:40, 6.0)	8m 35s
Verify tests pass (registry.fedoraproject.org/fedora:40, 8.0)	9m 16s
Verify tests pass (registry.fedoraproject.org/fedora:rawhide, 6.0)	8m 32s
Verify tests pass (registry.fedoraproject.org/fedora:rawhide, 8.0)	8m 32s
Verify tests pass (registry.access.redhat.com/ubi8, 6.0)	7m 48s
Verify tests pass (registry.access.redhat.com/ubi8, 8.0)	8m 45s
Verify tests pass (registry.access.redhat.com/ubi9, 6.0)	7m 29s
Verify tests pass (registry.access.redhat.com/ubi9, 8.0)	8m 45s
	2h 6m 52s

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