libvirt: Raise minimum supported version

machine-driver-libvirt was recently switched to 8.0.0:
crc-org/machine-driver-libvirt@bd62139

This fixes #4047

Signed-off-by: Christophe Fergeau <cfergeau@redhat.com>

pkg/crc/preflight/preflight_checks_linux.go

@@ -27,7 +27,7 @@ import (
 
 const (
 	// This is defined in https://github.com/crc-org/machine-driver-libvirt/blob/master/go.mod#L5
-	minSupportedLibvirtVersion = "3.4.0"
+	minSupportedLibvirtVersion = "8.0.0"
 )
 
 func checkRunningInsideWSL2() error {