quadlet: Drop the SocketActivated key

This was added in the old quadlet to work around issues with podman
not passing on notify fds and pids. However, these are now fixed with:

https://github.com/containers/podman/pull/11316
https://github.com/openSUSE/catatonit/pull/15

So, remove this key (which was never in a podman release anyway)

Signed-off-by: Alexander Larsson <alexl@redhat.com>

test/e2e/quadlet_test.go

@@ -287,7 +287,6 @@ var _ = Describe("quadlet system generator", func() {
 		Entry("readonly-notmpfs.container", "readonly-notmpfs.container"),
 		Entry("readwrite.container", "readwrite.container"),
 		Entry("readwrite-notmpfs.container", "readwrite-notmpfs.container"),
-		Entry("socketactivated.container", "socketactivated.container"),
 		Entry("timezone.container", "timezone.container"),
 		Entry("user.container", "user.container"),
 		Entry("user-host.container", "user-host.container"),